ONYCHOPHORA 285 



selves have the same origin. Only the tubules corresponding to the 

 jaws and the first three trunk appendages disappear. 



The sexes are separate in Peripatus and the gonads paired, but the 

 ducts unite to form a median passage opening just before the anus. 

 In the male the filiform spermatozoa are bound up in spermatophores 

 in the upper part of the vas deferens ; the lower part is muscular and 

 ejaculatory in function. Fertilization is internal. The ovaries are 

 embraced by a funnel, the receptaculum ovorum, which communi- 



Fig. 206. Diagram of transverse sections through embryos of Peripatus 

 capsnsis to show the haemocoele and the coelom in the following stages : A, 

 before the haemocoele has appeared; B, when the somite has divided into 

 dorsal and ventral parts ; C, when these parts have separated and the heart is 

 formed ; D, at time of hatching. After Sedgwick, i , alimentary canal ; 2, coelom 

 (cavity of mesoblastic somite, dividing into 2 cavity of gonad and 2, coelomic 

 part of excretory tubule ; in C and D the tubule is shown divided into 2', 

 coelomic sac and 2', canal); 3, haemocoele, 3', heart. 



cates with an oval receptaculum seminis. The eggs are fertilized then 

 at the proximal end of the oviduct : they vary in size according to the 

 species. In the larger, development takes place at the expense of the 

 yolk and the secretions of the uterine wall; but the embryos from 

 smaller eggs become attached to the uterine wall and a placenta is 

 formed. 



There are other derivatives of the ectoderm, the coxal glands (not 

 homologous with those of arachnids), found on all the legs except 



