DEVELOPMENT WITHOUT ACTUAL YOLK-SAC. 



27i 



which gives rise to the retractor of the funnel. We thus see here 

 again that the funnel forms in much the same way in other forms. 



The course of development 



of the other organs, such as /^^^ di 



the gills and the intestine, the /f * 



otoeysts and the eyes, can be " ^ 



made out by reference to Figs. I,-" 



1_M) and 127, as they resemble, r , 



in their origin and development, 

 the similar structures in Loligo. 

 The arms, on the contrary, 

 must be referred to more in 

 detail, since, according to 

 GKENACHEB'S statement, they 

 appear in an order somewhat 

 different from that seen in 

 Lai i.<i<> vu.lytiri*. We have 

 already mentioned two pairs of 

 arms at an earlier stage, and 

 there was some uncertainty as 

 to the presence of a third pair, 

 which in any case soon follows 



-tr. 

 ----run. 





ds. 



FIG. 127. Older stage of GKENACHER'S 

 Cephalopod embryo, seen obliquely from 

 the anal side (after GRENACHER). , 

 anus ; 2 and .., rudiments of the second 

 and the third pairs of arms ; on the latter 

 are seen bulgiugs which perhaps lead to 

 the formation of the fourth pair ; o,b, optic 

 vesicle ; au, rudiment of eye ; ch, chro- 

 matohores'. ds, yolk-sac ; go, optic 



ganglion ; km, nuchal (collar-) muscle ; 

 lateral portion of the funnel ; k, rudiment 

 of gill ; ma, mantle ; of., otocyst ; rt, re- 

 tractor of the funnel ; tr, funnel ; wk, 

 " white body ". 



the others. Of these pairs of 



arms, those which appeared first 



are s?iid to be the more dorsal 



in position. At the base of the 



sul INC.] unit third pair a fourth 



grows out, diverging to a certain extent from it. A fifth pair has not 



been observed in this Cephalopod, but probably develops later. 



If GRENACHER is correct in his statements, the arms, in this Cephalopod, 

 appear in an order the reverse of that which prevails in Loligo and Se}na. A 

 certain departure from the accepted order was also found in the Loligo 

 examined by BROOKS (p. 263). We must await further observations, made 

 for preference on related forms, to solve this difficulty. We shall not attempt 

 to describe the arms of this Cephalopod embryo, although the difference in 

 si/.i- between them and those of the embryos of Loligo in younger stages 

 (p. 261) seems to demand examination, and the different result as to the order 

 of appearance of the arms in GRENACHER'S embryo might thus be attained. 



In consequence of the small amount of yolk they contain, the 

 embryos soon resemble the adult in the shape of the body more 

 rln>i'ly than do those of other Cephalopods. The embryo depicted in 



