76 CHIMyEROID FISHES AND THEIR DEVELOPMENT. 



far forward, almost to the end of the embryonic gut, the band of fusion extending 

 in a narrow zone as denoted at x, fig. 69 n. (3) The concentration of the yolk- 

 entoblast under the embryonic body; this becomes conspicuous quite in front of the 

 embryonic gut, then merges with the gut, then separates from it, and, as the lumen 

 of the gut opens out ventrally, it proceeds backward in a layer finally rounding 



H 



D 



F 



Fig. 69 A-M. Transverse sections through early embryo and neighboring blastoderm of stage corresponding to that of plate V, 



fig. 35. The series passes from in front backward. 



C, Yolk region intruding between caudal folds ; <!<*, gut cavity; '", mesoblast; :V, yolk lying in cavity of gut ; 

 X, fold near posterior end of embryo where ectoderm and entoderm merge. 



outward on either side. (4) The presence in the cavity of the embryonic gut of 

 small masses of the disintegrating segments of the egg (fig. 69 G, gc), which serve 

 probably as food, interesting in connection with the fate of the yolk in Chimsera 

 (cf. in stages of Plate vm). Contrasting the foregoing conditions with those in an 

 elasmobranch in stage B (e. g., as shown by the Zieglers, Archiv f. mikr. Anatomic, 



