PHYLUM ARTHROPOD A. 



resemble the parents except in size and colour. In P. capensis the 

 period of gestation is thirteen months. 



(b] 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. It 

 is probable that the spermatozoa bore in through the skin, as in some 

 leeches. 



While it is characteristic of Arthropods, in which the develop- 

 ment of chitin is so predominant, 

 that ciliated epithelium is absent, it 

 seems that in Peripatits, which is 

 much less chitinous than the others, 

 ciliated cells occur in some parts of 

 the reproductive ducts. 



Development. There is some 

 variety of development in different 

 species. Thus there is much yolk 

 in the ovum of P. nova zealandiie, 

 extremely little in that of /'. 

 capensis. 



In P. capensis the "segmenta- 

 tion " is remarkable, for true cleav- 

 age of cells does not occur. The 

 fully "segmented" ovum does not 

 exhibit the usual cell limits. It is 

 a protoplastic mass or syncytium 

 with many nuclei. Even when 

 the body is formed, the continuity 

 of cells persists, nor does the adult 

 lack traces of it. To Mr. Sedg- 

 wick this singular fact suggested the 

 theory that the Metazoa may have 

 FIG. 147. Embryos of Peripatus begun as multinucleate Infusorian- 



capensis, showing closure of 

 blastopore and curvature of 

 embryo. After Korschelt and 

 Heider. 



a., Anus; /., blastopore; ///. 

 />.s., primitive segments ; n> 

 proliferation. 



closed 



like animals. 



The gut appears from a fusion 

 of vacuoles within the multinucleated 

 mass, and a gastrula stage is thus 

 mouth ; established. A very interesting 

 , zone of feature is that the blastopore or 

 mouth of the gastrula is first elon- 

 gated, then dumb-bell shaped, then 

 the two ends which form the mouth and the 



except at 

 anus. 



In the ova of P. novic zealanduc, which have much yolk, a superficial 

 multiplication of nuclei forms a sort of blastoderm, which spreads over 

 almost the entire ovum. The segmentation in this case has been called 

 centrolecithal (the type characteristic of Arthropods), but it is again 

 true that for a long time the cells do not exist as well-defined units. It 

 has been said, indeed, that "the embryo is formed by a process of 



