EXPLANATION OF PLATES Til, IV, AND V. 



lum, both of nucleus and cell-substance, slightly stained. Greatest diameter 

 •03 mm. Borax carmine^ sublimate and acetic. Zeiss's f, oc. 2, camera. 



Fig. 4. — Three nuclei from endoderm of embryo of Peripatus capensis 

 of stage of Pt. 1, PI. II, fig. 19. Zeiss's r, oc. 2, camera. 



Fig. 5. — Nucleus of endoderm cell, lying in the gut of an embryo of the 

 same stage. Zeiss's f, oc. 2, camera. 



Fig. 6. — Two endoderm masses of Peripatus capensis, with their con- 

 nections and processes. Surface view of sublimate preparation as seen with 

 Zeiss's Jjth oil imm., oc. 2. Sublimate and acetic. 



Fig. 7. — Surface view of a portion of the reticulum connecting the endo- 

 derm masses and ectoderm of a fully segmented ovum of Peripatus 

 capensis, as seen with a Zeiss's Jgth oil imm. No endoderm masses shown. 

 Sublimate preparation. Strongly refractile bodies in the strands of the net- 

 work and sometimes in the meshes. 



Fig. 8. — Transverse section through the fertilised ovum of Peripatus 

 capensis, showing the nucleus in the spherical stage. The protoplasmic 

 network around the nucleus is denser than elsewhere. A well-marked cavity 

 in the centre of the ovum. Nuclear network for the most part unstained. 

 Nuclear membrane and extra-nuclear reticulum stained. Diameter of nucleus 

 "04 mm. Borax carmine, picric acid. 



Fig. 8a. — Nucleus of the last. The lithographer has not been successful in 

 either of these figures, in reproducing the fine intra-nuclear network of the 

 original. 



Fig. 9. — Portion of edge of ectoderm of Peripatus capensis, with 

 adjacent endoderm masses showing connection between the two. Surface 

 view of sublimate preparation, as seen with Zeiss's c, oc. 2. 



Fig. 10. — Ideal diagrammatic transverse section through the fully segmented 

 ovum of Peripatus capensis, at about the stage figured in PI. I, fig. 8, 

 ec. Ectoderm, en. Endoderm masses, connected by reticulum, e. s. Egg-shell. 



Fig. 11. — Transverse section through an ovum of Peripatus capensis 

 with two segments. The section passes through the centre of the nucleus of 

 one segment. The nucleus has the spindle form, which immediately precedes 

 division. The figure shows clearly the continuity and the similarity between 

 the fibres of the spindle and the fibres of the extra-nuclear reticulum. A 

 well-marked cavity is present in each segment. Greatest diameter of spindle 

 •06 mm. Drawn with Zeiss's F, oc. 2, camera. Sublimate and acetic. 



Fig. 12. — Portion of edge of ectoderm of ovum of Peripatus capensis, 

 almost at the close of segmentation, as seen with a Zeiss's water imm. 2. 

 Sublimate preparation. The connection between the ectoderm cells is clearly 

 shown, also between the ectoderm cells and the network connecting the 

 endoderm masses. Nucleus of ectoderm indicated. n. Network. The 

 apparent granulation of the ectoderm is caused by the fineness of the 

 reticulum. 



Fig. 13. — View of endoderm mass of an ovum of Peripatus Balfouri, 



