Historical concepts of the medusoid of Millepora spp. and Hickson's follies

Dick Randall, my mentor at the University of Guam Marine Laboratory, alerted me to Sydney Hickson's having mangled the systematics of Millepora spp., in the early days of my study.   Hickson, the ultimate lumper decided to spell it Millepora sp.(1)   He had determined that all of the then-known species of Millepora were eco-variants of a single Atlantic species, Millepora alcicornis.  Hullbrandt Boschma, decades later, restored sanity to the taxonomic picture of the group  but the grand synonymization of Hickson lives on as a footnote in taxonomic history.

This was far from the only blasphemy conducted by Hickson.  I will not treat here his fantastical description of the developmental cell biology of Millepora sp., which, to be fair, he retracted in a succeeding publication.  But in his error of judgement about the structure of the medusoid of Millepora spp. Hickson promulgated a misconception of a different kind: his drawing of the medusoida  portrayed a deformed, post-spawning individual, apparently turned inside-out, possibly dead.  This erroneous image was co-opted at some point as a component of a representation of the structure of Millepora spp., based upon the remarkable line drawing from H. N. Moseley's reports from the Challenger Expedition.   The composite has propagated through almost every textbook of Invertebrate Zoology until recently, illustrating the medusa (or, more properly, medusoid) swimming above the cross section of the colony. 

If Hickson committed an absurdly erroneous lumping the species of Millepora, another chapter in the history of misunderstandings of  the medusoid of Millepora spp. involves an over-zealous splitting. In his tome, a taxonomy of the medusae of the world, Mayer had split the medusae of Millepora spp.---as the Medusae Milleporinae---out from all other hydrozoan medusae, the "veiled medusae,"  on account of its purported absence of a velum (veil).  A question remains: did Hickson originate this misconception as well?   

 I was thrilled when I collected medusae (or medusoids) of Millepora platyphylla in April, 1985, I was able to observe them in a dish, at the University of Guam Marine Laboratory.  Luckily, Professor Lucius Eldredge was on hand, and I asked him to check whether they had a velum; he  verified the presence of a velum.   The medusae I observed had not yet spawned.  It was immediately apparent that they differed substantially from the drawing I had seen, I think from Hickson.  It seemed to me that the configuration of the medusae in Hickson's drawing would be that of a spent individual---one that had already expelled its gametes. 

Mangan or Duerden may have been the last person to report observing medusae of Millepora alcicornis., in 1909 or 1910.  

Hickson wove a fantastical tale based on misinterpretations 

I just re-read Hickson's fantasy analysis of the reproductive biology of Millepora plicata, based on a remarkable degree of mis-interpretation of histology.  He weaves an entirely fantastical tale of the origin of the ovum, it's development, internal fertilization (which does not happen at all), and growth of a larva and it's expulsion.  

My blog post does not treat of this.  It is incredible.  Literally.  I am not suggesting you read it, but cite it here.  In his favor, he was indeed prolific, and he ultimately retracted this story.  But it's not the only issue among Hickson's publications.  Or among the other leading lights of Zoology in the latter part of the 19th Century who failed to critically examine or repeat his work, but built entire new stories upon Hickson's foundation.  

Hickson SJ. VIII. On the sexual cells and the early stages in the development of millepora plicata. Philosophical Transactions of the Royal Society of London.(B.). 1888 Dec 31(179):193-204

  

It is tempting to suggest that Sydney Hickson, one of the most prominent marine zoologists of his day (around the turn of the 19th to the 20th century), as a charlatan.   Indeed, one of my long-languishing projects has been to track down the life of the anomalous drawing of Medusae Milleporinae and prove whether he was the originator of this long-lived false cartoon of the medusa of Millepora spp.  After reading through one of his anatomical studies recently, I have come to appreciate what a remarkable observer he was.  However, he certainly suffered from a massive level of presumption.  

And, in a sense, it's a reflection of the nature of Zoology of that era, that he was so highly respected as a zoological authority that his errors persisted for so long, without being tested.  This reflects badly upon the assumption that science proceeds by the testing of hypotheses.  And re-testing.  Hickson obviously took the massive level of respect he enjoyed to heart.  

In Chuukese, there is a word that applies: baatá.  This verb refers to persons who takes flattery to heart.  An example would be a boy who, having been singled out as a good basketball player, goes out and buys basketball gear, and inhabits the cloak of the praise he has enjoyed.  In Chuuk, this is taken to a remarkable extreme: one can "abaatá" (cause to baatá) another person through disingenuous flattery.  

Hickson is an unfortunate example of someone whose entire body of work is perfused with the fruits of his baatá.  But it is on the greater community that he was placed on such a pedestal. 

Another example is found in a previous post of mine: https://millepora.blogspot.com/2022/10/an-obscure-mention-of-millepora-work-by.html

(1)  spp. designated multiple species; sp. a single species, though it be unnamed.  I will use the correct "spp." herein.

ADDENDA

  As I searched via google (scholar?), an amazing thing happened: I saw my on name

  on a Google citation, from a mailing list thread of many years ago.  

  Remarkably, I had written about Hickson's blunders in a post to a

  microscopy mailing list (which, I need to determine).  

Davis, A. E. (2002). Microscopic Artifacts In The History Of Biology. Microscopy Today, 10(2), 18-21.

I had discussed the issue of Hickson's fantasy development cycle, referring to it as a consequence of microscopic artifacts.  Artifacts have been referred to as   “artificial structure(s) or tissue alteration(s) on a prepared microscopic slide as a result of an extraneous factor.”  

From my query on that mailing list:

(About) Sydney Hickson's early work on Millepora spp. (Cnidaria:Hydrozoa) fire corals. It seems an incredible lapse, a wholly fabricated natural history account, one that persisted for a considerable period in the fabric of the mythology of biological knowledge. I am interested because reproduction of Millepora platyphylla is the subject of incompleted thesis research of mine.

Hickson published a report on reproduction of "Millepora" around the end of the 19th Century. ... In this report, which I do not have available at this time, he included several plates of drawings depicting a putative sequence of reproductive events in this organism. We now understand that his depiction is not even close to the way that Millepora spp. (which were later redesignated as proper individual species through painstaking work by Boschma-notwithstanding the issues recently raised by molecular work) reproduce.  The depiction involved dozens of drawings, and a sequence of events based on a misinterpretation of what are apparently artifacts....

Also,.   

... Hickson's erroneous drawings of the meduse of Millepora lived on for over 3/4 of a century in virtually every Invertebrate Zoology textbook published until the late 1980s or 1990s. His erroneous description of the medusa of Millepora as lacking a velum led to the designation of a separate branch of hydromedusae by Mayer, as the only hydrozoan medusa without a velum. My unpublished observations in the 1980s as well as published observations by John Lewis of McGill University showed that the medusae of Millepora spp. clearly possess a velum. I apologize for monopolizing the bandwidth. I hope this is as fascinating a topic for others as for myself, and not considered off-topic.

  

In 1900 Hickson was able to examine material that included medusoids.  The following is a correction in his paper on the subject,, wherein he reported on these findings.  

Hickson, Sydney John. "The medusae of Millepora." Proceedings of the Royal Society of London 66.424-433 (1900): 3-10. 

Correction.—In a former communication to the Royal Society, 1 described certain cells in the cenosarc of Millepore from Celebes as ova. Since the discovery of the female medusa, I have carefully re-examined my preparations, and satisfied myself that I made a mistake. These cells are not ova, but the cells which ultimately give rise to the large kind of nematocyst.

 

My earliest introduction to Millepora spp.

 Professor Richard Randall had been disallowed from being an MSc thesis advisor by the big shots at the University of Guam Marine Laboratory, I think unfairly.  

Shortly after I had arrived on Guam to begin graduate studies in Early August of 1984,  Dick Randall made himself known to me by stopping to offer me a ride down the hill to the Laboratory, and introducing himself as a coral biologist (he is also a geologist).  Immediately he engaged me in discussion of ideas for a thesis topic. 

I explained that I was interested in reproductive periodicity in Tridacnid clams, particularly in endocrine control of gametogenesis.  Such a study would necessarily involve elucidating the phenology, the seasonality, indeed, every aspect of the timing of reproductive events.  This topic was a huge turn-on for me.   

 

  At that point he introduced me to Millepora spp., the fire corals.  He explained that the Calcium Carbonate hard parts of these corals bore outward evidence of reproductive status---the Ampullae that sheltered the medusae within them.  Thus, it seemed, it would be possible to study the reproductive periodicity by the most expedient of all possible methods: examination of hard parts over time.  

(Professor Lu Eldredge stood in his stead.  It is on me and me alone that I did not complete the thesis that was required to earn an MSc from UJ. of Guam.  Had there been a plan B, I would certainly have the MSc. degree today.  Dick Randall deserved to be treated with more respect, as I might add.

So it was I started collecting fragments of Millepora spp.   At that time, I took every opportunity to snorkel, and each time I did I collected at least one fragment of Millepora spp., usually M. platyphylla.  That first term, I was enrolled in a statistics class; I hoped I would be able to draw some conclusions using some statistical means or another on the timing of reproductive efforts.  I had learned from R. K. Trench at UCSB about Tridacnids.  and the interesting variations in the patterns of timing.  I had hoped to be able to study neurosecretory control of gametogenesis of the giant clams.  This interesting twist regarding the biology of Millepora would provide an opportunity to complete a study on the side, in my spare time, no sweat, while engaged in other pursuits.

Professor Randall kept a large plastic tank of Calcium Hypochlorite out on the lanai behind his lab/office, for cleaning corals.  I gradually built up a number of bleached coral specimens, but had not recognized ampullae.  Perhaps I would be able to find time later on to examine the coral skeletons and create a database.

Dick warned me about the work of Sydney Hickson, a prominent british zoologist of the late 19th Century---one of the big names.  Hickson had made the error of synonymizing all species of the genus Millepora as a single species, M. alcicornis, an Atlantic species found prominently in the Caribbean.  Boschma would, much later, correct the record in  a series of long papers on the specific characters, and revised the systematics of the genus.  

When I first laid eyes on the medusae of Millepora platyphylla, I was on the beach at Toguan Bay, Guam.  it was obvious to me that the illustrations by Hickson of the medusa of Millepora had also promulgated an egregious error; this illustration was widely disseminated, as part of a revised drawing of Moseley in most Invertebrate Textbooks.

An obscure mention of Millepora work by Hickson: "double disappearance" of germinal vesicle (I think)

 By happenstance, I stumbled upon a paper---which I would never otherwise have encountered---on Peripatus, with a single reference about a mention by Hickson of Millepora.  I am curious.  Bercause I am uncertain of the meaning of all of this, I include the small section (about 2 pp) from that paper.

Sheldon, L., 1889. The Maturation of the Ovum in the Cape and New Zealand Species of Peripatus. Studies from the Morphological Laboratory in the University of Cambridge, 4, p.275.

 

The reference is to:

HICKSON, S. J.-- " On the Sexual Cells and the Early Stages in the
Development of Millepora plicata," Phil. Trans.,' 1888

The following is from Sheldon:

Disappearance of the Germinal Vesicle.
The existence of a stage in the ripening of the ovum in
which no nucleus is visible has now been described in almost
all eggs whose maturation has been at all completely investi
gated. In many of these cases the mode of disappearance has
not been observed , but in most of those in which the process
has been seen it is similar to that which I have described in
Peripatus capensis and P. Balfouri, namely, that the
nucleus loses its round shape, its outline becomes irregular,
and by the loss of its membrane its contents mingle with and
finally become indistinguishable from the protoplasm of the
egg.
Between this stage and that at which the nucleus is
again visible, when it is small and in the spindle stage about
to bud off the second polar body, there is no trace of the ger
minal vesicle in the ovum.
I wish here to draw attention to
the fact that my observations were made on complete series of
sections of well-preserved ova, so that the probability of my
having overlooked it is not great. This mode of disappearance
has been described by Henking (10) in Phalangeden, and by
Stuhlmann (17) in a considerable number of insects. The
loss of the nuclear membrane is also described by Scharff (13)
as occurring in some osseous fishes, although he does not state
that all trace of the nucleus disappears. Lankester (12) also
describes a stage in the ovum of Sepia in which no germinal
vesicle is present .
Blochmann (5) describes in Neritina fluviatilis the loss
of the nuclear membrane, and consequent mingling of the
nucleo- and egg-plasma, but states that the germinal spot
remains, and, breaking up, gives rise to the chromatin of the
nuclear plate. This certainly cannot be the case in the Cape296
LILIAN SHELDON.
species of Peripatus, since the germinal spot disappears before
the germinal vesicle.
Stuhlmann suggests that the disappearance may have some
connection with the presence of yolk in the egg, since he has
observed it in all insect eggs in which yolk is present in large
quantities, but not in Aphides and Cecidomya, in which yolk
is absent. Its disappearance in Peripatus capensis , how
ever, in which no yolk is present, goes against this theory,
unless it is to be regarded as a survival from the time when yolk
was present in the ovum .
On the other hand, it is supported
>
by the observations of Will (20) and Scharff (13) , who state
that some of the yolk is derived from the germinal vesicle,
and by the phenomena which I have described in P. novæ
zealandiæ ; but these points will be discussed later under
the Formation of the Yolk .
Stuhlmann ( 17) has not observed the disappearance of the
germinal vesicle in P. Edwardsii , but this may be due to the
incompleteness of his researches in this species .
The double disappearance of the germinal vesicle in P. novæ
zealandiæ is, so far as I know, unparalleled, and I am unable
to offer any explanation of it. The first disappearance seems
to be that which is homologous with that which commonly
occurs in ova, and its mode of disappearance will be discussed
later on. The details of the second disappearance are quite
unknown, and at first sight it would appear that the nucleus
shown in the ovum in fig . 30 was the first segmentation
nucleus ; but that this is not the case seems certain from the
fact that a large proportion of the unsegmented ova which were
found in the uterus were without any nucleus, and it is not
easy to conclude that this condition was abnormal since the
ova were found in several different parents, and were preserved
in several ways . The only case in which, so far as I know , a
double disappearance has been described, is that of Millepora,
in which Mr. Hickson ( 11) states that the nucleus is dispersed
before and after the formation of the polar bodies ; but since
in P. novæ - zealandiæ I have observed no polar bodies, it
is not possible to compare the two cases .

 

 

Colored figures from Hickson

I am cautious about Hickson for a couple of reasons.  But he did so much!  I should point out a couple of things:

 Hickson's description and drawing of the medusa of Millepora does not reflect the actual appearance of the medusae I have seen. It appears to be of a female medusa that is in the process of expelling it's cargo of ova.  That illustration has been borne by many of not most Invertebrate Textbooks, as a minor revision of that from Moseley's work, probably drawn by J.J. Wilde, Challenger artist.  All of that is another story.

Another extreme example of Hickson's lack of caution was his synonymizing all Millepora species as one: M. alcicornis.  

In my mind his work on the reproductive physiology and anatomy of Millepora spp. suspect.  One of the volumes replete with illustrations, needs to be studied: I think he got reproduction COMPLETELY wrong for Millepora spp.  To be fair, he may have corrected this error in a later publication.

 I still think that his abundant visual expositions of Histology of Millepora are worth study, especially for one like myself who is just learning.  Caution is the watchword.

 These images were captured from Google Books's of

Hickson, S.J., 1891. The Medusae of Millepora Murrayi and the Gonophores of Allopora and Distichopora,"'Quart. Journ. Micr. Sci.,'xxxii.

 

This seems to be a unique copy, with colored figures.  Possibly colored by hand?

 

Calicoblast layer under dactylozoid

 

Clustering proliferation of dividing symbiotic dinoflagellates in Millepora sp. medusa/egg

 I will post this image for now, and get back to it.  These symbionts infect or are drawn into the medusa/egg before liberation from the mother colony.  As far as I have seen, all medusae of a given colony are either male or female.  The larva is pre-charged with it's symbionts.   The order and nature of events during the infection process are of great interest.  

From a stack of 9 images.

Annotated image to demonstrate the dividing cells with two nuclei.  Other cells, more visible in the image above, are near enough that perhaps they are just recently divided.

Ongoing imaging explorations

Millepora platyphylla: interface between medusa and ampulla. 

Phase contrast

 

I was exploring phase contrast with a new--to me--used Zeiss Plan Ph2 40/0.65 160/0.17 objective.  This slide was stained using Cason Trichrome stain.  

This shows a part of a medusa, with scarcely developed ova.  I think most of will contribute themselves to the growth of the three, or possibly, sometimes, four ova that eventually develop.  These may be called nurse cells?  

A meshwork of vacuolated material---lipid droplets---is being traversed by some zooxanthellae.  The eggs of Millepora spp. are hosts to symbiotic dinoflagellates (zooxanthellae) before their release and fertilization.  This is part of the process.

 

 The ampulla is a hollow vessel that holds the medusa as it develops.  The tissue outside the medusa is apparently related to the ampulla.  Intense yellow indicates calicoblastic tissue.  I am interested that in this image the yellow resolves into green and yellow particles; I wonder, does this point to two separate structures involved in producing---and in this species sometimes dissolving?---Calcium Carbonate.  To my knowledge the structural changes involved in generation of ampullae, in conjunction with growth of the medusae and development of the gametes in both male and female medusae has not been worked out in its entirety.  The reproductive events, per se, have been studied closely.