DETAILED ACCOUNT OF PERIPATUS. 



of the uterus by what has been called a " placenta," so suggestive is it of 

 mammalian gestation. The older embryos lose this " placenta," but 

 each lies constricted off from its neighbours. When born the young 

 resemble the parents except in size and colour. In P. novce zealandice, 

 the ova pass from the ovary into the uterus in December, and the young 

 are born in July a long period of gestation. 



(d) Male (of P. edwardsii]. The male elements are produced in small 

 testes, pass thence into two seminal vesicles, and onwards by two vasa 

 deferentia into a long single ejaculatory duct, which opens in front of the 

 anus. In the ejaculatory duct the spermatozoa are made into a long 



packet or spermatophore, which 

 is attached to the female during 

 copulation. 



[While it is characteristic of 

 Arthropods, in which the de- 

 velopment of chitin is so pre- 

 dominant, that ciliated epi- 

 thelium is absent, it seems that 

 in Peripatus, which is much less 

 chitinous than the others, ciliated 

 cells occur in some parts of the 

 reproductive ducts, and perhaps 

 also at the internal funnels of 

 the nephridia. This is indeed 

 what one would expect.] 



Development of Peripatus. 

 There is a strange variety of 

 development in different species 

 of this genus. Thus there is 

 much yolk in the ovum of P. 

 novce zealandice, extremely little 

 in that of P. capensis. In the 

 former species the yolk has a 

 manifold origin ; it is said to 

 arise in the protoplasm or the 

 ovum itself from the breaking 

 up of the germinal vesicle, from 

 surrounding follicle cells, and 

 from yolk present within the 

 ovary. In P. capensis and P. 

 a, Anus ; bl, blastopore ; m, mouth ; balfouri spermatozoa reach the 

 &.i?e SeSmentS; "" 2 ne f vary, anS there probably the 



ova are fertilised, but in P. novce 



zealandice the spermatozoa are confined to the receptaculum seminis, 

 near which fertilisation seems to occur. In the maturation of the ova 

 of P. capensis and P. balfouri two polar bodies are extruded as usual, 

 but none have been observed in the case of P. novce zealandice. 



In P. capensis the " segmentation " is remarkable, for true cleavage of 



cells does not occur. The fully "segmented" ovum does not exhibit 



the usual cell limits. It is a protoplasmic mass or syncytium with 



many nuclei. Even when the body is formed, the continuity of cells 



19 



7 



FlG. 94. Embryos of Peripatus 

 capensis, showing closure of blas- 

 topore and curvature of embryo. 

 (After KORSCHELT and HEIDER.) 



