DETAILED ACCOUNT OF PERIPATUS. 



289 



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 bom the young 

 resemble the parents except in size and colour. In P. novie zealandia, 

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

 are born in July — a long period of gestation. 



(b) yiaXs (oi 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. 

 novti^ zealandiiE^ extremely little 

 in that of P. capeusis. 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. 

 balfo^iri spermatozoa reach the 

 ovary, and there probably the 

 ova are fertilised, but in P. nov(B 



Fig. 94. — Embryos of Feripaliis 

 capeitsis, showing closure of blas- 

 topore and curvature of embryo. 

 (After KoRSCHEi.T and Heider.) 



a, Anus ; 5/, blastopore ; ;;?, mouth ; 

 ps, primitive segments ; w, zone of 

 proliferation. 



zealandiiB the spermatozoa are confined to the receptaculum seminis, 

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

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

 but none have been observed in the case of P. tiova 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 



