OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 239 



5. Gentoo Penguin Embryo, 16 Days. (Fig. 14.) 

 The embryo was small, the nails were not developed, so far as could be seen on 

 naked-eye examination. There was a well-marked ridge down the centre of the 

 abdomen and thorax. The toes did not appear beyond the web, but looked more as if 

 they were embedded in it. The fourth toe appeared as if the web were continued 

 round it. 



Duck Embryo, 1G Days. 

 As for 15 days. Down more marked. 



6. Gentoo Penguin Embryo, 17 Days. (Fig. 15.) 



The embryo was in good condition and the fully formed integument was complete. 

 The skin was marked by papillae regularly arranged. On either side of the tail there 

 were several down fibres varying from 1*7 mm. in length to a length just visible to the 

 naked eye. 



Duck Embryo, 17 Days. 



The down was well developed. 



7. Gentoo Penguin Embryo, 18 Days. (Fig. 19.) 

 This specimen was somewhat macerated. 



Duck Embryo, 18 Days. 

 Embryo completely down-covered. 



8. Adelia Penguin Embryo, 19 Days. 



The embryo was fully formed, the integument was complete. There was a well- 

 marked median groove over the abdomen and thorax, and from it on either side 

 extended twelve transverse grooves. The body was completely naked except for eight 

 fibres on the tail (four on either side of the median line). 



9. Gentoo Penguin Embryo, 19 Days. 



The embryo was fully formed, and the integumentary covering was complete. 

 There were no transverse grooves on the abdomen. 



10. Gentoo Penguin Embryo, 20 Days. 



The embryo was fully flexed and completely devoid of down. The integument over 

 the abdomen was not quite complete. A bare area in length "28 cm. and in breadth 

 at base "07 cm. extended forward in front of the umbilicus. There were no transverse 

 grooves*on the abdomen. 



TKANS. KOY. SOC. EDIN, VOL. XLVII. PAET II. (NO. 10). 35 



