EXPLANATION OF PLATES IIIj Iv, AND V. 



as seen with a Zeiss's water imm. 2, to show the spongework of which the 

 mass is composed. 



Pig. 14. — Transverse section through an oyum ofPeripatus capensis 

 with eight ectoderm cells, to show the greater density of the network round 

 the nucleus thau at the periphery, where it is continued into the reticulum of 

 the next cell. Endodermal masses not indicated. Zeiss's D, oc. 2, camera. 

 Diagrammatic. 



Fig. 15. — Transverse section through an ovum of Peripatus capensis 

 with about sixteen ectoderm cells, somewhat diagrammatic. The endoderm is 

 indicated. The section shows that the ovum is of the nature of a hollow 

 blastosphere. Zeiss's D, oc. 2, camera. 



EiG. 16. — Section through an embryo of Peripatus capensis at the 

 stage of PI. I, fig. 11. The endoderm masses contain a central denser 

 protoplasm, and a number of darkly-staining granules. No nuclei visible 

 in endoderm. Zeiss's d, oc. 2, camera. 



Fig. 17. — Transverse section through the uterus, and contained a fully 

 segmented ovum of Peripatus capensis (blastosphere stage). Zeiss's c, 

 oc. 2, camera. ec. Ectoderm. en. Eudoderm, u. e. Uterine epithelium. 

 e. s. Egg-shell. 



Fig. 18. — Slightly oblique section through an embryo of Peripatus 

 capensis of the stage of PI. I, fig. 15. Zeiss's c, oc. 2, camera. 



Fig. 19.— Portion of ovum of Peripatus Balfouri with eight ectoderm 

 cells, showing one of the corner ectoderm cells connected by a reticulum 

 with two endoderm masses. The endoderm masses contain a large number of 

 irregularly-shaped yellowish bodies, s. b.; a few of the latter are present in 

 the ectoderm. The outer parts of the ectoderm cells were much vacuolated, 

 and gradually passed into the reticulum connecting them with the endoderm 

 masses. The endoderm was in two main masses, and two or three smaller 

 pieces in the network between ectoderm and endoderm. 



Fig. 20. — Transverse section through an embryo of Peripatus capensis 

 slightly older than the stage of PI. I, fig. 15. The endoderm is largely 

 vacuolated, and only a rudiment of the gut-cavity is present. Zeiss's D, oc. 

 2, camera. 



Fig. 21. — Section behind the blastopore of same stage as Fig. 23, showing 

 the most conspicuous part of the polar area. Zeiss's imm. 2, oc. 2, camera. 



Fig. 22, «, b, c— Series of sections behind the blastopore of an embryo of 



Peripatus capensis, slightly older than that from which series Fig. 24 were 



taken. Beginning of formation of primitive streak. Zeiss's D, oc. 2, camera. 



a. Second or third section behind blastopore. Polar area marked by a 



slight groove, its nuclei beginning to increase. 

 h. Five sections behind blastopore. Groove absent, but increase of 



nuclei shown. 

 c. Twelve sections behind blastopore, p. a. Polar area. 



