NO. 1783. NORTH AMERICAX LERX.^OPODID.^— WILSON. 219 



The nervous system, therefore, is practically all concentrated in 

 the infra-oesophageal ganglion, since the part above the gullet is 

 hardh' swollen more than enough to serve as the origin of the nerves 

 that arise from it. In this respect the Lernseopodidse present a 

 strong contrast to the Ergasilidae and Caligidge, as also to the free- 

 swimming forms. 



The infra-oesophageal ganglion is made up of a peripheral layer of 

 nerve cells and a central mass of fibers. The cells are evenly dis- 

 tributed over the outer portion of the ganglion and are not bunched 

 at the origin of the nerves. 



There are a very few cells in the commissures at the sides of the 

 oesophagus and in the supra-oesophageal ganglion, but the great 

 mass of both these portions is fibrous, and nothing but fibers can be 

 found in any of the nerve trunks or branches. 



REPRODUCTIVE ORGANS. 



The beginnings of the reproductive organs are shown in both sexes 

 at this second copepodid stage. The ovaries and testes are paired 

 and lie in what may be termed the small of the back, between the 

 stomach and the dorsal body wall and just behind the median maxilli- 

 pedal gland (t, fig. 32 and o, fig. 33). The ovaries begin as small 

 spherical masses of cells, not very definitely arranged, but gathered 

 together on either side of the midline (o, fig. 36). From the posterior 

 end of each is given off a slender oviduct which runs around the 

 stomach wall to the ventral surface and then backward to the open- 

 ing in the side of the genital segment. At intervals along the duct 

 are gathered rounded masses of cells wliich later develop into the 

 uterine processes, within which the eggs are matured (up.). At the 

 posterior end of the duct is an irregular cellular mass in which may 

 be distinguished the beginnings of the cement gland (eg.), its duct 

 being corkscrew-shaped at this stage. Between these two masses 

 in the center of the body is another cellular accretion which later 

 develops into the semen receptacle and its ducts. 



As the sex organs mature the posterior portion of the body of the 

 female increases greath' in size, especially lateralh', leaving large 

 spaces on either side of the digestive tract. These are filled as fast 

 as the}' are formed by the increased convolutions of the oviduct and 

 especially b}' the development of the uterine processes anteriorly 

 and the large cement glands posteriorly. Claus evidenth' did not see 

 either the ovaries or the testes of Aclitheres percarum. The bodies 

 which he has designated as such are a long distance back of their 

 true position, as revealed in serial sections. In the living larvae as 

 well as in the adults the sex organs are so situated as to be invisible 

 from the exterior. But certain portions of the convolutions of the 

 oviducts and vasa deferentia come close to the body wall and are 

 easily distinguished. And these are what Claus has designated as 

 the organs themselves. 



