1885.] The Development of Peripatus Capensis. 355 



in our autumn, when the males deposit spermatophors quite casually 

 all over the body of the female, and continue to do so until about 

 January (perhaps a little later). 



The ovaries always contain spermatozoa, but in smaller numbers, 

 directly after the eggs have passed into the oviduct, than at any other 

 time. 



How the spermatozoa pass up the uterus and oviducts, which are 

 always full of embryos, generally containing as many as thirty to 

 forty, I do not know. 



Fertilisation is apparently effected in the ovary. The fertilised 

 ova pass into the oviduct in April, while the uterus is still full of 

 embryos almost ready for birth. Segmentation and the early stages 

 of development take place in the oviduct, where the eggs remain until 

 May, when the young are born. They then pass into the uterus to 

 remain there until the following May. 



The ripe ovum is elliptical in shape, and of a dark colour by trans- 

 mitted light. The opacity is due to the presence of granules (food 

 yolk). It is enclosed, when in the oviduct and uterus, by a trans- 

 parent structureless membrane, which is derived apparently from the 

 follicular cells surrounding the ovarian ovum. 



Segmentation is complete. The first furrow is in the transverse 

 plane of the ovum and divides it into two halves. The second furrow 

 is at right angles to the first, and divides each of the first formed 

 segments into two. Then each segment divides into two, one small 

 and one large segment. There are thus four small segments lying 

 close together on one side of the egg and four large segments. The 

 former give rise to the ectoderm, and the latter to the endoderm. 

 The subsequent division of these two kinds of cells proceeds inde- 

 pendently. At the end of the segmentation, the ovum consists of a 

 number of large endoderm cells scattered irregularly within the egg 

 membrane, while the ectoderm cells form a mosaic of cells closely 

 applied together and placed close to the membrane on one side at 

 about the middle of the long axis of the egg. 



The endoderm cells now draw together and form a solid mass of 

 cells on which the ectoderm rests like a cap. 



The ectoderm then grows round the endoderm cells, and completely 

 encloses them, excepting at one point (opposite to that on which the 

 ectoderm cap was placed). 



The embryo thus acquires a spherical form, and consists of a solid 

 gastrula, the small uncovered spot of endoderm constituting the 

 blastopore. 



A cavity then appears in the centre of the endoderm cells, and this 

 cavity opens to the exterior through the blastopore. 



The embryo now becomes slightly elliptical, and the blastopore 

 also elongates in the direction of the long axis. 



