248 



MR HAROLD AXEL HAIG ON 



phases are at all comparable in the two cases, then the present foetus should have 

 completed about one-third of its development. In many respects, however, this 

 foetus shows an advance upon the three-months human embryo, notably in connection 

 with the pituitary gland, the cerebellum, and the internal ear. 



(ii.) The other mammals (rabbit, cat, and pig) with which incidentally the foetus 

 has been compared show on the whole a fairly close agreement, both anatomically 

 and histologically ; one marked exception, from the anatomical point of view, is in 

 connection with the kidney, which places the Seals in a small sub-group of the 

 carnivora, to which the bear also belongs. 



(iii.) The developmental features of the pituitary, kidney, and brain are sufficiently 

 instructive to necessitate, when possible, investigation of the earlier phases of 

 development of these organs ; the acquisition of early Seal embryos is, however, a 

 difficult matter, but they might with advantage be sought for, as large numbers of 

 Seals are killed annually. 



In conclusion, the author wishes to thank Dr. W. S. Bruce and Professor 

 Waterston for their courtesy in lending Scotia specimens of foetal Seals for investi- 

 gation ; also Professor Hepburn for many valuable suggestions in connection with 

 anatomical details, and Mr. T. H. Burlend, of University College, Cardiff, for much 

 useful criticism concerning the arrangement of the above report. 



BIBLIOGRAPHY. 



Bailey and Miller, Text-book of Embryology, 1909. 



Bryce, T. H, Quain's Anatomy : vol. i., Embryology. 



Chievitz, Archiv Anat. u. EmbryoL, Supplement, 1897. 



Grosser, Vergleich. Anat. und Entwickelungsgeschichte der Eihaute u. Placenta, 1909. 



Haig, Trans. Roy. Soc. Edin., ibid. 



Hepburn, Trans. Roy. Soc. Edin., vol. xlviii., 1913. 



Herring, Journ. of Exper. Physiol., 1909. 



Hertwig, Handbuch der Entwickelungslehre der Wirbeltiere, 1906. 



Keibel and Mall, Text-book of Embryology, 1912. 



Schafer, E. A., Quain's Anatomy : vol. ii. part, i., Text-book of Microscopic Anatomy. 



EXPLANATION OF PLATES. 



Plate XIX. 



Fig. 1. Foetus of the Sea-Leopard Seal :- 

 a.f. Anterior nipper. 

 p.f. Posterior flipper. 



t. Tail. 

 cl.a. Cloacal aperture. 



u. Umbilicus. 

 u.c. Umbilical cord. 



am. Amnion. 

 p. Placenta. 

 b. Tongue : the bifid extremity showing 



between lips. 

 pal.f. Palpebral fissure. 



