The entry says that the Natural History Museum published its report on the three embryos in 1934, in ten pages, price two shillings, and that it found nothing of what the journey had been made to find. The custodians follows the embryos from Cape Evans to the deaths of the two professors who had them. This piece is about the report itself, and what has been learned since about the two claims the journey rested on.

Parsons, 1934

The British Museum (Natural History) published the scientific results of the Terra Nova expedition in parts between 1914 and 1935. Zoology, volume IV, number 7, “Penguin Embryos”, by C. W. Parsons, lecturer in zoology in the University of Glasgow, with two plates and three text-figures, pages 253 to 262, is dated September 1934 and was priced at two shillings. A note in the bound volume says that twenty-five copies were printed on special paper. Parsons had written a report two years earlier on penguin embryos collected by the Discovery Investigations in the 1920s, and so came to Wilson’s three with a series of gentoo and chinstrap embryos already described, which is the point he makes at the end.

He began with the history. The Discovery of 1901 to 1904 had brought back fifteen emperor eggs of which four held undecomposed embryos and only one of those was not fully incubated, so “it was imperative therefore to revisit the rookery early in the breeding season of the bird, if the hope of obtaining a collection of embryos to show a series of stages in its development was to be realised. Wilson fully understood the scientific importance of acquiring such a collection and also the almost insuperable difficulties in the way of its attainment.” The site “is such that it is practically inaccessible. Its approaches are guarded by ice pressure ridges presenting the utmost difficulty in negotiation even in the full light of summer, and in the winter darkness seemingly impassable. Nevertheless, when the opportunity presented itself—in the course of the ‘Terra Nova’ Expedition—he did not hesitate to make the attempt.” The journey “was successful to the extent of obtaining three eggs containing embryos that were partly incubated. In due course these passed into the hands of Dr. Assheton, and after his death into those of the late Professor Cossar Ewart.”

Then the material. The embryos had been numbered 1, 2 and 3 by size, 1 the smallest. The report on the emperor embryos “is based upon the sectioned material specified, and on the head of embryo No. 2”, which Parsons took out of its wax, soaked in formalin for some days to harden the brain, and dissected. “Unfortunately the preservation of the material is unsatisfactory. As Dr. Assheton remarks in his notes on embryo No. 2, ‘the epidermis has separated from the dermis in most places, preservation none too good, but very much better than that of embryo No. 1.’ The serial sections of embryo No. 1 bear out this statement fully. In them the brain is almost entirely absent and the sections, which were cut sagittally, are torn and distorted along the line of the top of the head. Only the cartilage remains in position.” The body sections of the smallest embryo “correspond closely with sections similarly cut of a fowl embryo of approximately eleven days incubation and call therefore for no special comment”; the youngest emperor “had reached a stage in development far enough advanced to possess a four-chambered heart and lungs actively budding air sacs”.

On the ages: the feather papillae were “present only in the tail region of the youngest embryo, but in the two older specimens they spread over the body in countless numbers”, a difference seen in gentoo embryos “which compare with fowl embryos incubated for approximately ten and thirteen days respectively”. “It is fair to conclude, therefore, that the stages represented do not indicate a considerable time interval between the two extremes, and that the morphological similarity between them, especially between embryos 2 and 3, is very close indeed.” Embryo 3 was half a millimetre longer than embryo 2. “They do not differ from one another probably by more than a day of incubation, and their morphological differences are superficial and trifling”, so that “it is justifiable to treat the two embryos as one for the purposes of comment.”

What he could say of the emperor embryo was that it was a penguin embryo. The wing cartilages of the smallest did not yet show the adult penguin’s fused bones, though the humerus already had the triangular end that Lowe had described as the penguin’s; the free metatarsals of the foot were “a feature which is generally agreed to be representative of a primitive condition”. The feather papillae “consist of simple thickenings of the dermis with a thin epidermis overlaying them similar in type to those described in Gentoo penguin embryos … and there is no reason to suppose that their subsequent history is in any way different.” The one thing that struck him was the head: “In comparison with other penguin embryos at the same stage of development—an Adelie embryo for example—the most striking feature of the Emperor embryo is not its size, but the high dome of the head”, which on dissection proved to be a mass of loose tissue round the pineal body; the brain itself showed “no exceptional features”. The viscera were “not different in any important particular from embryos of other species of penguin at the same stage”.

The scales came up in the second part of the report, on thirteen Adélie embryos the expedition had also collected, which gave him the series the emperors could not. In the oldest of these “the skin of the feet is marked with papillae resembling feather papillae. It is known, however, that they are in fact the precursors of the horny ‘scales’ of the feet, and it has been shown elsewhere (Cossar Ewart, 1922) that such papillae never do develop into feathers. This is remarkable because the close morphological relationship between feathers and scales seems to be perfectly well established on other evidence. Feather papillae and scale papillae must still be regarded, then, as being distinct from one another from the beginning, and corroboration of this opinion is provided by the sequence of the events in development. In contrast with the feather papillae, the scale papillae are late in making their first appearance. This would not be so if the feathers developed in the course of evolution from scales of the same kind as those which are conspicuous on the legs of adult penguins, and the explanation of the anomaly probably is that the horny scales protecting the feet of penguins and of other birds are epidermal structures of a secondary nature that are fundamentally different from reptilian scales which are the true ancestors of feathers.”

His concluding remarks are the Museum’s verdict on the experiment, and they are quoted here whole. “Taking a broad view of the facts as they have been adduced, both from a consideration of the unique group of three Emperor penguin embryos and of the series of Adelie embryos, it must be stated that neither has greatly added to our knowledge of penguin embryology. At the time when the collections were made the material brought back by more recent expeditions was not, of course, at hand, and the embryos on which the work of the present report is based had the advantage of priority. This advantage was lost owing to the death of two investigators into whose hands the material had been given, and in the meantime other collections were made which enabled the foundations of our knowledge of the subject to be laid.” The Adélie series shed “no new light upon the problem of penguin ancestry, however, and unfortunately nothing decisive could be expected from the collection of three Emperor embryos so close to one another in development as those that Dr. Wilson and his comrades obtained at such cost.” He allowed himself one small point for the other side: the embryo penguin keeps a slender tail longer in development than the embryo fowl does, “and this persistence of a primitive character is suggestive”. He thanked Professor Graham Kerr and Dr Percy Lowe, “and the authorities of the British Museum for the loan of the material”.

What the rocks said

Lowe, of the Museum’s bird room, had published in 1933 a long paper “On the Primitive Characters of the Penguins, and their Bearing on the Phylogeny of Birds”, which argued the position Wilson had lectured on in 1911: that penguins had never flown and had branched off near the root of the birds. That argument did not survive the fossils. In 1946 George Gaylord Simpson of the American Museum of Natural History published “Fossil Penguins”, a review of every fossil penguin then known, and concluded that penguins descend from flying birds, with no land-dwelling stage between. In 2006 Kerryn Slack and colleagues described four skeletons from the Waipara Greensand of New Zealand, a Paleocene bed lying just above the boundary that marks the end of the dinosaurs, and named the genus Waimanu. At 61 to 62 million years it is the oldest penguin known, and it was already a flightless diver; the authors used it to date the split between penguins and their nearest flying relatives, and from that to argue that the modern birds had already begun to diversify before the end of the Cretaceous. The emperor is not the nearest approach to a primitive bird. It is a late, large, specialised member of a line that lost flight at least sixty million years ago and had flying ancestors before that.

Where feathers came from was answered without an egg. From 1996 the Yixian Formation of Liaoning in China began to give up dinosaurs that were not birds but carried feathers, beginning with Sinosauropteryx, a small theropod with a fringe of simple filaments along its back, described in Nature in 1998. The question Ewart had asked of the papillae was reopened by developmental biologists, and in 2002 Richard Prum and Alan Brush, reviewing the way a feather grows inside its follicle, concluded that the feather was not an elongated or frayed scale but an evolutionary novelty, a tube grown from a new kind of follicle, whose stages of complexity could be read in the fossils from Liaoning. Ewart’s “fundamentally different”, written from three emperor embryos and a tray of goose eggs in Edinburgh, had been on the right side of the question.

Tring

The Museum’s bird collection is at Tring in Hertfordshire, and its egg collection, more than a million eggs, is there. The Museum’s own page on the collection lists “one of the three Emperor Penguin eggs collected by Dr Edward Adrian Wilson, Apsley Cherry-Garrard and Henry Bowers in July 1911” during “the Winter Journey to Cape Crozier”. A Museum feature of March 2018 on the egg collection tells the story in a paragraph, with a photograph of three emperor eggs captioned as those of 1911, with holes made in them to let the embryos out, and says that Cherry-Garrard “delivered the embryos and eggshells to the Museum on his behalf in the summer of 1913”. The Museum’s Treasures gallery at South Kensington shows “an emperor penguin egg collected during Robert Falcon Scott’s Antarctic expedition” among its chosen specimens. The sections Assheton cut, and the head Parsons took out of its wax, are not mentioned on any public page, and this piece does not know where they are.

Sources

• C. W. Parsons, “Penguin Embryos”, British Antarctic (“Terra Nova”) Expedition, 1910. Natural History Report. Zoology, Vol. IV, No. 7, pp. 253–262, September 1934. archive.org
• P. R. Lowe, “On the Primitive Characters of the Penguins, and their Bearing on the Phylogeny of Birds”, Proceedings of the Zoological Society of London, 1933, pp. 483–538, as cited by Parsons.
• George Gaylord Simpson, “Fossil Penguins”, Bulletin of the American Museum of Natural History 87, article 1, 1946. AMNH library
• Kerryn E. Slack and others, “Early Penguin Fossils, plus Mitochondrial Genomes, Calibrate Avian Evolution”, Molecular Biology and Evolution 23 (2006), 1144–1155. doi.org
• Pei-ji Chen, Zhi-ming Dong and Shuo-nan Zhen, “An exceptionally well-preserved theropod dinosaur from the Yixian Formation of China”, Nature 391 (1998), 147–152; Richard O. Prum and Alan H. Brush, “The Evolutionary Origin and Diversification of Feathers”, Quarterly Review of Biology 77 (2002), 261–295. doi.org, doi.org
• Natural History Museum: Katie Pavid, “A journey through the largest egg collection in the world”, March 2018; “Bird egg and nest collections”; “Treasures in the Cadogan gallery: emperor penguin egg”. nhm.ac.uk, eggs and nests, treasures