630 



AVES KIHDS. 



Fig. 292, 



in 



293. 



(706.) Although the above description gives the reader a ge- 

 neral view of the process 

 of oviparous generation 

 in its most perfect and 

 consequently most com- 

 plex form, the reader, in 

 applying it to the deve- 

 lopement of the ovum in 

 the inferior OVIPARA, 

 must bear in mind the 

 following important dif- 

 ferences : 1st. That in 

 the air-breathing REPTI- 

 LIA the white of the egg 

 is almost, if not entirely, 

 wanting; but the other 

 phenomena are similar to 

 those witnessed in the 

 Bird. 2dly. That 

 FISHES not only 

 is there no white 

 formed, but for ob- 

 vious reasons the 

 allantoid apparatus 

 is not developed. 

 The egg in these 

 lower tribes con- 

 tains only the yolk 

 and the cicatricu- 

 la ; it swells from 

 absorbing the sur- 

 rounding water, 

 and the fetus is 

 developed upon 

 the surface of the 

 yolk ; the latter, 

 which, as in Birds, 

 communicates with 

 the intestine, be- 

 ing slowly received 

 into the abdomi- 

 nal cavity. 



