236 SCIENCE PROGRESS 



In " The Corpus Luteum in the Ovary of the Domestic 

 Fowl " (Am. Journ. Anat. vol. xxiii. January 191 8) Pearl and 

 Boring give an interesting account of this gland in a bird 

 and state that it is derived from theca interna. It is nor- 

 mally connected with ovulation, and homologous with the 

 similar structure in mammals. The same authors also dis- 

 cuss the external characters, behaviour, anatomy, and cytology 

 of " Hermaphrodite Birds " (Journ. Exp. Zool. vol. xxv. 

 February 191 8). The eight specimens studied were all basally 

 females, and it was noticed that the interstitial cells had no 

 causal relation to the secondary sex characters, whereas the 

 degree of external femaleness was precisely correlated with 

 the amount of lutear cells or pigment ; the sex or degree of 

 activity of the gonad has no direct causal relation to the deve- 

 lopment of comb, spurs, and wattles. 



Other papers include : " Vestigeal Gill Filaments in Chick 

 Embryos, with a Note on Similar Structures in Reptiles," by 

 Boyden (Am. Journ. Anat. vol. xxiii. January 191 8) ; " The 

 Effect of the Heart-beat upon the Development of the Vascular 

 System in the Chick," by Chapman (ibid.). 



Sugita continues his " Comparative Studies on the Growth 

 of the Cerebral Cortex, 3. On the Size and Shape of the 

 Cerebrum in the Norway Rat (Mus norvegicus), and a com- 

 parison of these with the corresponding characters in the 

 Albino Rat. And 4. On the Thickness of the Cerebral Cortex 

 in the Albino Rat " (Journ. Comp. Neur. vol. xxix. February 

 191 8). At the same age the brain of the Norway rat is heavier 

 than that of the albino, and it is also slightly longer, wider, 

 and higher. Its volume is about 21 per cent, above that of 

 the albino, but its specific gravity is less. The cerebral cortex 

 is slightly thicker in the Norway, particularly in the region of 

 the occiput, a condition probably correlated with the somewhat 

 better development of the eye and the visual apparatus. The 

 lower percentage of water in the albino is perhaps related to 

 smaller amount of grey matter. An instructive analysis of 

 the time relations between menstrual age, copulation age, 

 ovulation age, and fertilisation age of human embryos is 

 given by Mall in a note " On the Age of Human Embryos " 

 (Am. Journ. Anat. vol. xxiii. March 191 8). Apparently the 

 average time between copulation and fertilisation is one day. 



Other papers include : " Advantages of Sagittal Sections 



