BSTABLttHMjan 01 MM r\ni;v\i. fOBM '!' Tin: BODY. 203 



hand a tubular >heath. which is continii" , place hy means. 



of a connecting cord with tin- liar .-lining prti. 



cloth. 



A process similar to the externally visible one just descri I <!, by 



\vliich the lateral ami ventral walls of the holy are produced from 

 the >heet-like fundaments, takes place at the same time within the 

 embryo in the splanchnopleure. Tiiere are developed from it, as 

 i'lnlii the >o m atople lire, an Ulterior, a pOfteriar, and two la'eral 

 intestinal folds. 



Fii>t. at the time when the head is differentiated i tig. 122), the 



part of tlie splanchnopleure corresponding to it (F.Xj>.) i> folded 



her into a tube, the so-called curtly of the fore gut or ]i><i<l-<i nt (D). 



The Mine process repeats itself on the third day of incubation at 

 the posterior end of the embryonal fundament, where, upon the 

 appearance of the caudal part (Plate I., fig. 11), there is formed 

 within it ami out of the splanchnopleure the cavity of the hind <jnt. 



Both parts of the intestine at first terminate with blind ends 

 directed toward the outer surface of the body. At the head-end 

 the mouth-opening is still wanting, at the po>trrior nd the anus. 

 \Vh n, however, one raises the blastoderm with the nascent embryo 

 from the yolk, and examines it from the under side, the anterior 

 and posterior portions of the intestinal canal exhibit openings (*//</' 

 and //'///). through which one can look from the yolk-side into the 

 blind-ending cavities. One of these is called the anterior, the other 

 the posterior, intestinal portal or intestinal entrance (Plate I., fig. 11 

 ?v/y//';<nd It<ljif). 



Between the two portals the middle region of the intestinal canal 

 remains for a long time as a leaf-like fundament. Then by its 

 becoming somewhat bent downwards (Plate I., figs. 9 and 2) there 

 s under the chorda dorsal is an intestinal groove (//), which lies- 

 bet ween fore and hind gut. Owing to the further increase of the 

 lateral int>tinal folds (df), the groove becomes deeper and L 

 and finally, by the approximation of the edges of the folds from in 

 front, from behind, and from both sides, becomes cl>s d into a tube 

 in the same manner as the wall of the body. 



At only one small place, which is indicatd by the ring-like line 

 ilit in Plate I., figs. Sand 10, the folding and constrict ing-oil' process 

 is not complehd, and h. re the intestinal tube too remains con- 

 tinuous, by means of a hollow >talk. with the extra-embryonic part 

 of the splanchnopleure, which em-loses the yolk. 



The part of the germ-layers which is not employed in the formation 



