610 



ZOOLOGY 



SECT. 



with one another throughout the body to the posterior end, where 

 they join together behind the anal aperture. A number of very 

 fine transverse commissures, more numerous than the segments, 

 (i.e., than the pairs of limbs) connect the two cords together to 

 form a ladder-like nervous system comparable to that of some 

 of the Flat Worms. The cords are very slightly swollen opposite 

 each pair of limbs : nerve-cells cover them uniformly throughout 

 their entire length. The brain gives off nerves to the antennae. 

 The nerves to the jaws are just where the brain passes into the 

 longitudinal nerve cords. 



The excretory organs are nephridia (Fig. 483) of the type of 

 those of the Annulata, situated in pairs in the lateral compartments 

 of the body-cavity, and opening on the lower surfaces of the legs at 

 their bases. Each nephridium consists of a thin-walled closed 



internal vesicle, a looped 

 tube (s.c), and a dilated ter- 

 minal vesicle (s.), situated 

 close to the external open- 

 ing. The salivary glands 

 and the reproductive ducts 

 are, as shown by the study 

 of their development, speci- 

 ally modified nephridia, as 

 apparently also are a pair 

 of glands — the anal glands 

 — opening close to the anus. 

 Reproductive organs. 

 — Peripatus has the sexes 

 distinct. In the female 

 there are two tubular 

 ovaries and two uteri, the 

 latter in the form of long 

 curved tubes which unite behind in a median vagina opening on 

 the exterior on the ventral surface just behind the anus, between 

 the legs of the last pair or behind them. In the oviparous forms 

 the opening is situated at the end of a long cylindrical process — 

 the ovipositor. In some species, connected with each uterus where 

 it leaves the ovary, are two diverticula — the reeeptaculnm seminis 

 and receptacuhtm ovorum. In certain species one or other of 

 these may be absent. 



In the male there are two tubular testes, each with a narrow vas 

 efferens opening by a funnel-like aperture into a vcsicula seminalis ; 

 this is followed by a long, narrow, coiled vas deferens. The two 

 vasa deferentia unite together to form a median tube — the ductus 

 ejaculatorius — opening on the exterior, in the same position as the 

 vagina of the female. The wall of the proximal part of the 

 ejaculatory duct is glandular, and secretes a. substance forming 



Fio. 483.— PeripatUS capensis, nephridium fruin 

 the ninth pair of legs, o.s, external opening ; 

 p.f', internal opening into the lateral compartment 

 of the body-cavity ; s, vesicle of nephridium ; 

 s.e. 1, s.e. 2, s.c. 3, s.c. 4, successive regions of 

 coiled portion ; s.o.t., third portion of nephridium 

 broken off at p.f from the internal vesicle, which 

 is not shown. (From the Camb. Nat. Hist., after 

 Balfour.) 



