INDEX. 655 



influence of on early development, stalk of, 142; general account of, 161; 



282, 283 circulation of, 162 ; later history of, 164 



Yolk-sack, Amphibia, 108, 115, 116; en- Yolk-sack of Elasmobranchii, enclosure 



closure of, 101 of, 51, 236 ; circulation of, 52 



Yolk-sack, development of in Eabbit, 188 ; Yolk-sack of Lacerta, 173; circulation of, 



of Mammalia reduced, 188; circulation 173 



of in Eabbit,'_193 ; [enclosure of in Sauro- Yolk-sack, Teleostei, 61, 65 ; enclosure of, 



psida, 240 " 60 ; circulation of, 66 

 Yolk-sack, enclosure of, Petromyzon, 70 



Yolk-sack, Lepidosteus, 97 Zona radiata, villi of, 195 



Yolk-sack of Chick, enclosure of, 133 ; Zonula of Zinn, 407 



