1108 president's address. 



I'ead before the Royal Society on the 17th of March last. In this, 

 as is now pretty generally known through the medium of various 

 scientific or quasi-scientific journals, he gives a history of previous 

 theories and investigations and his own discoveries, which are 

 summarized as follows — 



In Monotremata and Marsupialia — 



I. — There is a vitelline membrane which, appearing between the 

 young ovum and follicular epithelium, persists until hatching in 

 Monotremata, and until late uterine stages in Marsupialia. 



II. — There is a second primary egg membrane secreted by the 

 follicular epithelium shortly before the ovum leaves the ovarian 

 follicle — the pro-albumen. 



III. — The pro-albumen, by absorption of fluid in the Fallopian 

 tube and uterus, becomes the albumen layer outside the vitelline 

 membrane. 



IV. — A secondary egg membrane — the shell membrane — -is 

 found in the Fallopian tubes, and becomes thicker in the uterus. 



V. — The albumen soon disappears, and the vitelline membrane 

 comes to lie next the shell. 



VI. — The ovum absorbs fluid from the uterus, and increases in 

 Monotremes from about .3 mm. to 15 x 13 mm. 



VII. — A layer, simulating the appearance of a membrane, inside 

 the vitelline membrane is a coagulum formed by re-agents from 

 the nutritive fluid passing into the ovum. 



VIII. — There is a germinal disc, and the ovum undergoes a 

 partial segmentation in Monotremes and Phascolarctos. 



In Placentalia — 



IX. — The vitelline membrane has generally been known as part 

 of the zona pellucida. 



X. — The pro-albumen is probably represented by the outer 

 " granular layer " of the zona pellucida. 



