ONCHYOPHOKA OR PROTOTRACHEATA. 



305 



parts being invaginations of the ectoderm. Nephridia are not known in 

 any other Tracheate. The salivary glands and the genital ducts seem to 

 be modified nephridia. It may be noted, too, that the same is perhaps 

 true of the "coxal glands" of Linmhis and of the antennary glands 

 of Crustaceans. 



Coxal or crural glands lie in the legs and open to the exterior. They 

 can be in part evaginated, and they probably help in respiration. In 

 the male of P. capcnsis the last pair are very long (Fig. 146, a.g, ). The 

 large mucus glands, which pour forth slime from the oral papilla?, are 

 regarded as modified crural glands. 



Reproductive system. (a) Female (of/ 3 , eihvardsii}. From the 

 two ovaries, which are surrounded by one connective tissue sheath, and 

 arise, as usual, from the coelomic epithelium, the ova pass by two long 



oc.co 



FlG. 146. Dissection of Peripatus. After Balfour. 



a*., Antennae; or.p., oral papillas ; e.g., cerebral ganglia; sl.d.. 

 duct of slime gland (sl.g.) ', s.o.S, eighth segmental organ or 

 nephridium ; v.c. , ventral nerve connected by transverse com- 

 missures (co.) with its fellow ; s.o.i"/, seventeenth nephridium ; 

 g.o., genital aperture ; A., anus ; p.d.c., posterior commissure ; 

 f.ij, seventeenth appendage ; a.g., last crural gland, that of 

 the opposite side is marked v.g. ', F.I, F.2, first and second 

 legs; oe.co., oesophageal nerve commissure; oe., oesophagus; 

 ph., pharynx, the remainder of the gut is removed. 



ducts leading to a common terminal vagina opening between the second 

 last legs. These ducts are for the most part uteri, but on what may be 

 called the oviduct portions adjoining the ovaries, there are two pairs of 

 pouches a pair of receptacula seminis (for storing the spermatozoa 

 received during copulation), and a pair of receptacula ovorum for storing 

 fertilised eggs. 



The eggs are hatched in the uteri, and all stages are there to be found 

 in regular order. The young embryos seem to be connected to the wall 

 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 



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