REPORT ON PENGUIN EMBRYOS 



COLLECTED DURING THE 



DISCOVERY INVESTIGATIONS 



By C. W. Parsons, B.A. 



Lecturer in Zoology in the University of Glasgow 

 Text-figs. 1-9, Plates I-VI 



INTRODUCTION 



OUR knowledge of the development of birds is securely based on the detailed in- 

 vestigations that have been made of the embryology of the common fowl. Amongst 

 an exceptionally long list of modern workers who devoted their attention to the problems 

 involved some names stand out pre-eminently. F. M. Balfour was publishing on the 

 subject in 1873, Duval gave us his Atlas d'Embryologie in 1889, Keibel and Abraham 

 pubhshed the Normentofel in 1900, and in 1908 Lillie brought out his Development oj 

 the Chick. 



The last-mentioned books give evidence of the massive research extending over 

 twenty years on chick embryology, and it is surprising that in this period comparatively 

 few other species of birds were the object of similar enquiries. The duck naturally 

 had a place in the work of embryologists — next to the fowl it is the most accessible 

 material — and of less common forms penguin embryos have been the subject of a certain 

 amount of published work. Material brought home by the Scottish National Antarctic 

 Expedition was worked out by Waterston and Geddes (1909), and other penguin embryos 

 collected by the Deuxieme Expedition Fran9aise were the basis of a joint report by 

 R. Anthony and L. Gain in 191 5. Their Contribution a V etude de Vembryologie des 

 Spheniscidae is devoted to three main points : (i) the development of the skeleton of the 

 wing, (ii) the development of the skeleton of the foot, (iii) the feathering ("pterylosis"). 



The embryos described by Waterston and Geddes were fixed in formalin and were 

 not in a satisfactory condition for microscopic examination in any great detail. The 

 limitations imposed by these conditions are of course very great, and the report, as far 

 as the embryos are concerned, deals chiefly with external features. There was therefore 

 an urgent need for new material, and during the Discovery investigations an extensive 

 collection of the embryos of two species of penguins was made in the course of the 

 1928-9 and 1 930-1 seasons. 



The majority of the embryos— sixty-four— were of the Gentoo penguin, Pygoscelis 

 papua, from South Georgia. The remainder— fourteen— were of the Ring penguin, 

 Pygoscelis antarctica, from the South Shetlands. They were obtained and preserved by 

 Mr F. C. Eraser, the eggs being taken at random and the embryos dissected off the 

 blastoderms by him and then fixed. He used two fixatives. In the 1928-9 season at 

 South Georgia only the eggs of Gentoo penguins were taken and twenty-six embrj'os 



