364 



THE RABBIT. 



stricted off from the rest of the blastodermic vesicle, in a manner 

 practically identical with that in which the embryo chick is con- 

 stricted off from the yolk-sac (cf. Figs. 145, 146, and 110, 112). 



By the end of the ninth day the rabbit embryo (Figs. 145, 146) 

 has acquired shape, structure, and proportions agreeing very 

 closely with those of a chick embryo of about the twenty-sixth 

 hour, with which it also corresponds almost exactly in size. 



Up to this stage the embryo has been practically straight 



TA 



AN 



C? 



BM 



AN 



FIG. 146. A median longitudinal, or sagittal, section through a Rabbit Embrj'o 

 and blastodermic vesicle at the end of the ninth day. (Cf. Fig. 145.) 

 (In part after Van Beneden and Julin.) x 10. 



AN, tail fold of ainnion. AN', proaiunion. BM, mid-brain. C, extra-embryonic part 

 of the coelom or body-cavity. CP, pericardial cavity. E, epiblast. E'. thickened epiblast 

 by which the blastodermic vesicle is attached to the uterus (cf. Pig. 169). EK, epiblastic 

 villi. GF, fore-gut. GH. hind-gut. GT, mid-gut, H, hypoblast. M, mesoblast. 

 SI, sinus terruinalis. TA. allantois. YS, cavity of yolk-sac, or blastodermic vesicle. 



(Fig. 146), lying with its dorsal surface upwards, towards the 

 wall of the uterus, and its ventral surface downwards towards 

 the yolk-sac. From this time, however, the dorsal surface of 

 the embryo grows more rapidly than the ventral surface, and the 

 whole embryo in consequence becomes strongly flexed. By the 

 end of the tenth day (Fig. 147), while the middle portion of the 



