DEVELOPMENT OF THE CAPE SPECIES OF PERIPATUS. 211 
with two endoderm masses. The endoderm masses contain a large number of 
irregularly-shaped yellowish bodies, s. 4.; 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. 
Fic. 20.—Transverse section through an embryo of Peripatus capensis 
slightly older than the stage of Pt. 1, Pl. XXXI, 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. 
Fie. 22, a, 6, 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. 
6. Five sections behind blastopore. Groove absent, but increase of 
nuclei shown. 
c. Twelve sections behind blastopore. jp. a. Polar area. 
Fie. 23.—Section through an embryo of Peripatus capensis at the 
gastrula stage (Pt. 1, Pl. XXXI, fig. 19). The gut-cavity is still traversed 
by a mass of much vacuolated endoderm. Zeiss’s D, oc. 2, camera. 0/. Blas- 
topore. g.g. Gut-cavity of gastrula. ec. Ectoderm. ez. Endoderm. 
Fic. 24, a—d.—Series of sections througha gastrulaof Peripatus capensis 
of stage Pt. 1, Pl. XXXI, fig. 21, before the appearance of the primitive 
streak. Zeiss’s D, oc. 2, camera. 
a. Five sections in front of blastopore, showing increase of nuclei between 
ectoderm and endoderm, similar to that which takes place at a later 
stage behind the blastopore. Endoderm cell lying loose in gut. 
6. Through middle of blastopore. Blastopore traversed by strands of 
protoplasm. 
c. Five sections behind blastopore, showing beginning of polar area in 
middle ventral line. 
d. Five sections behind last, through centre of polar area. 4/. Blasto- 
pore. p.a. Polar area. 
Fic. 25, a, b—Two sections behind blastopore of embryo of Peripatus 
capensis, slightly younger than Stage A (Pt. 1, Pl. XXXI, fig. 22). Harly 
primitive streak. No mesoblastic bands. Zeiss’s D, oc. 2, camera. 
a. Immediately behind blastopore. /. Marks position of blastopore in 
preceding section. 
b. Nine sections behind the preceding. Large increase of nuclei in polar 
