OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 41 



6, 9, or 12 days, it does not follow that the development has been proceeding for the 

 same number. 



Be this as it may, we found it necessary, especially in dealing with the early 

 specimens, to revise the sequence of specimens so as to avoid the absurdity of embryos 

 of an obviously earlier stage of development being classified as older than specimens 

 of a later stage. The number of days of incubation is, according to the series of 

 specimens, thirty. This is surprisingly short, and as there are some obvious gaps 

 in the series, we are not prepared to express an opinion as to whether it is correct 

 or not. 



The embryos were preserved in 2^ per cent, formalin, and we desire to place on 

 record our sense of real obligation to the collectors for the care and trouble which they 

 took, and for their great skill in packing the specimens, which alone is responsible for 

 the excellent state of preservation in which many of these exquisitely delicate specimens 

 were when put into our hands. 



As a result of the long time which elapsed between the date of collection and 

 examination and of the prolonged immersion of the specimens in formalin, it has not 

 been possible to carry out, satisfactorily, any very fine histological examination nor to 

 determine with absolute accuracy the exact date of the first appearance of the primary 

 ossific centres, the formalin, apparently, having exercised a slight decalcifying action. 

 Our investigations have, therefore, of necessity been somewhat restricted, and many 

 important problems in connection with the development of the penguin remain unsolved. 



In dealing with the embryology of the penguin the following points seemed to us 

 important : 



1. The enormous length of time through which the penguin has persisted without 

 undergoing important modification. In the Quart. Journ. Geol. Soc., vol. xv. p. 670, 

 Professor HUXLEY described a penguin of large size whose remains were obtained from 

 the pliocene strata of New Zealand. For the reception of this bird he established the 

 genus Palseeudyptes. 



It is exceedingly doubtful whether the establishment of a new genus was necessary, 

 and Professor MORRISON WATSON in his report on the anatomy of the Spheniscidse 

 (Challenger Report, vol. vii. p. 46), expresses the opinion that this pliocene bird 

 might very well be regarded as belonging to a species of the existing genus Eudyptes. 



From the outset, therefore, we were prepared to meet with some peculiarities of 

 development of a more primitive avian type than that obtaining in modern birds. 



2. The enormously high specialisation undergone by the forelimb of the penguin in 

 the course of which it has been transformed from an organ of serial to an organ of sub- 

 aqueous flight. 



3. The modification undergone by the cervical spine to secure sufficient water dis- 

 placement anteriorly to carry the head and heavy beak without fatigue during the long 

 ocean voyages which the penguins undertake. 



4. The skeletal arrangements necessitated by the quasi-erect attitude. 



(ROY. soc. EDIN. TRANS., VOL. XLTIL, . 227.) 



