EXPLANATION OF PLATES I AND II. 



Fig. 17. — Per. capensis. Side view of embryo. A few endoderm cells 

 exposed. 



Pig. 18. — Ventral view of same. 



Fig. 19. — Per. capensis. Gastrula stage, ventral view. Blastopore 

 distinctly circumscribed. Size •204 mm. X '24.0 mm. 



Fig. 20. — Side view of same in outline. 



Fig. 21. — Per. capensis. Gastrula stage, ventral view. Same stage as 

 Fig. 19, but embryo slightly more elongated. 



Fig. 22. — Per. capensis. Stage A, showing slightly elongated blasto- 

 pore with primitive streak at hind end. Greatest length "48 mm. a. Denotes 

 the anterior end. 



PLATE II. 



All the figures on this Plate are of embryos of Peripatus capensis. 



Figs. 23 — 27. — From the original drawings by Miss Balfour, a. Denotes 

 the anterior extremity. 



The remainder of the figures on this Plate from drawings by Mr. E. Wilson. 



Fig. 23. Stage between A and B. With three somites and elongated 

 blastopore. Length of embryo '7 mm., length of blastopore '45 mm. 



Fig. 24. Stage between A and B. With five somites. The blastopore is 

 closing in its middle portion. Length of embryo '74 mm., of blasto- 

 pore "46 mm. 



Fig. 25. Stage B. The blastopore has completely closed in its middle 

 portion and given rise to two openings, the embryonic mouth and anus. 

 The anterior pair of somites have moved to the front end of the body, 

 and the primitive groove is very marked. Length of embryo r32 mm. 



Fig. 26. Stage C. Embryo, in which the flexure of the hind end of the 

 body has begun ; with about thirteen somites. The remains of the 

 original blastopore are present as the mouth, placed between the second 

 pair of mesoblastic somites, and the anus, placed on the concavity of 

 the commencing tail flexure, and still removed from the hind end of 

 the body. Greatest length when lying on its back 1"12 mm. 



Fig. 27. Side view of same embryo. 

 Figs. 28 and 29. — Stage D (spiral stage). 



Fig. 28. A young embryo of this stage, viewed from the side. With 

 commencing antennae and dorsal projection (</). 



Fig. 29. Rather older embryo of same stage (end of spiral stage), side 

 view. Eyes (e) as pits. Jaws and postoral appendages sprouting. 

 Rudiments of eleven pairs of legs. Length from anterior end of head 

 to bend {d) 1-G mm. At. Antennae, d. Dorsal thickening, e. Eye. 

 j. Jaw. or. p. Oral papilla, p. s. Prseoral somite. 



