PLATE XIV 



I'MHRYOS. 



Figs. 1 86 — 197. — C. gracilis. 

 Figs. 198 — 210. — C. lei'inseni. 



Fig. 186. C. gracilis. — Two cell stage, mounted whole. 



Fig. 187. — Ventral view of an advanced embryo. 



Fig. 1S8. — Lateral view of a similar embryo: — b.c^-, position of collar-cavity. 



Fig. 189. — Optical frontal section of a similar embryo from the ventral side. The constrictions at the 



sides of the yolk ()'/•) correspond with those in which the collar-cavities lie in other preparations; 



V. inv., external aperture of the ventral invagination. 

 Fig. 190. — Actual frontal section, more highly magnifictl: — v. inv., dorsal wall of ventral invagination, 



cut tangentially (other sections of the same embryo are shewn in figs. 195, 196). 

 Fig. 191 — 194. — Transverse sections of a similar embryo. Fig. 191 is through the anterior sense-organ 



{s.o.); fig. 192, through the anterior part of the ventral invagination (v. inv.); fig. 193, through 



the collar-cavities [b.c.-] and the metasomatic cavities (b.c.^); and fig. 194, through the metaso- 



matic cavities (b.c.^). 

 Figs. 195, 196. — Horizontal sections of the individual shewn in fig. 190. 

 Fig. 195 is through the dorsal region of the embryo: — b.c.''-, collar-cavity. 



Fig. 196 is between fig. 195 and fig. 190: — vac, vacuolated ectoderm, extending as far as the two arrows. 

 Fig. 197. — Nearly median sagittal section of a similar embryo. The region of the posterior pit {post. p. 



is, however, cut somewhat frontally, so that both third body-cavities (b.c.''') are visible. The 



somewhat crumpled vitelline membrane [v. ni.) is seen, while between it and the ectoderm are 



what are probably excretory granules [exc). The anterior ectoderm between the two arrows has 



the vacuolated character shewn in fig. 190. 

 Figs. 198 — 210. C. levinseni. 

 Fig. 198. — Advanced embryo, seen obliquely from the dorsal side. The central yolk-mass (yk) has a 



lumen; the edge of the reflected part of the yolk is not easily seen where it crosses the central 



mass, but is probably correctly represented: — vac, vacuolated ectoderm, which in the embryos 



of this species contains numerous refractive bodies. 

 Fig. 199. — Another embryo, probably somewhat older than fig. 198, seen from the side. The embryo was 



found in a peristome, close to its orifice, and may have been about to be liberated. 

 Fig. 200. — Advanced embryo of unusual appearance, in which the vacuolated ectoderm {%>ac.) and the 



ventral thickening (v.t.) have together the appearance of the proboscis of the adult. 

 Fig. 201. — Obliquely sagittal section of an advanced embryo. The vacuolated ectoderm (i'«c.) is invaginated 



dorsally and in front. It is uncertain whether the collar-cavity is seen on the ventral side, which 



is turned to the right. A space (artificial?), which is also seen in fig. 202, occurs outside the 



basement-membrane yb. m.) at the anterior end. 

 Figs. 202 — 206. — Five .sections of a transverse series of a similar embryo. The limits between the second 



and third body-cavities are not obvious in this series. 

 Fig. 202. — Through the anterior end. 

 Fig. 203. — Through the anterior yolk-mass. 



Fig. 204. — Through the central yolk-mass, which is here encircled by the refiected part of the anterior yolk. 

 Fig. 205. • — Through the extreme posterior end of the ventral thickening. 

 Fig. 206. — Through the extreme posterior end of the anterior yolk-mass. 

 Fig. 207 — 210. — Four sections of a frontal series of an older embryo. 

 Fig. 207. — Through the entire area of the ventral thickening {v.t.). 

 P'ig. 208. — Near the ventral surface, but cutting the five coelomic spaces. 

 Fig. 209. — Through about the middle of the embryo. 

 Fig. 210. — Through the dorsal half of the embryo. 



\Figs. ipo — ipj ivere drazvn tvith Zeiss, D D Obj.; Jigs. 1S6 — iS() and igS — 210 with Zeiss, C. All lit 

 figures were reduced */ 



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