40 DR D. WATERSTON AND DR A. CAMPBELL GEDDES ON EMHRYO PENGUINS 



The suggestion that the pectoralis major is in reality a cutaneous muscle seems to 

 us to be not without interest in view of the occasional occurrence in man of the 

 abnormal muscle, sternalis. Sir WILLIAM TURNER has suggested that it is to be 

 regarded as a vestige of the panniculus carnosus. Professor D. J. CUNNINGHAM has 

 pointed out that there is considerable evidence to show that it is formed by a devia- 

 tion or dislocation of a portion of the pectoralis major ; Mr F. G. PARSONS has shown 

 that in rodents the panniculus carnosus possesses two strata, and that there is 

 evidence to show that in man the deeper stratum of the pauniculus forms the fascial 

 sheath over the external oblique and that possibly a portion of the sterno-mastoid is 

 derived from the same stratum. He has also shown that there are good reasons for 

 regarding the pectoralis major as derived from the panniculus. To these observations 

 we now add the facts of the anatomy of the penguin, which appear to us to suggest that 

 the apparently antagonistic views of Sir WILLIAM TURNER and Professor CUNNINGHAM 

 are in reality not opposed, but complementary. 



PART II. 



ON THE EMBRYOLOGY OF THE PENGUIN. 



INTRODUCTORY. 



As has been shown, the anatomy of the adult penguin has been previously very 

 completely described, and little remains to be added to complete our knowledge of it. 



Of the embryology, on the other hand, the existing knowledge is incomplete, owing 

 presumably to the great difficulty in bringing back the necessary material in a con- 

 dition which allows of a detailed examination being made. A small number of 

 embryos was collected by the Challenger Expedition, but the condition in which they 

 were received by Professor MORRISON WATSON rendered them useless for description. 



The material which was put into our hands consisted of a number of specimens each 

 one of which had been removed from its egg upon a different day of incubation. It 

 would, therefore, appear that we had a specimen for each 24 hours of development. In 

 one sense this was so, in another not. The method of collection which was of necessity 

 adopted was as follows : The nest was watched, and the eggs were marked with the 

 date of their first appearance and were subsequently collected upon the desired day. 

 The difficulties of so doing and the fallacies necessarily attendant upon it are obvious. 

 First, it was quite impossible for the observer to know in which of the 24 hours preced- 

 ing the marking the egg had been laid ; secondly, it is known to be no uncommon thing 

 for the males and females to fight for possession of their egg and for the privilege of 

 incubating it. In the course of these struggles the eggs are apt to be dropped and to 

 lie for some time directly upon the ice. The result of this must be to retard for a time 

 the processes of development, and therefore, although an egg may have been laid for 3, 



(ROY. soc. EDIN. TRANS., VOL. XLVII., 226.) 



