16 BRITISH COrEPODA. 



the female. In tlie Gyclopidce and Notodel'phyidce the 

 fifth feet are usually rudimentary and alike in both 

 sexes, and in the HarpacticidcB they take the form of 

 small, marginally setose, foliated expansions, slightly 

 different in the two sexes, but generally larger in the 

 female, in which sex they serve sometimes as a 

 covering and support for the external ovisacs. In 

 the semi-parasitic groups these organs are generally 

 small, 1- or 2-jointed, and alike in both sexes. 



The nervous system of the Copepoda is described as 

 consisting of a brain, which gives off various sensory 

 nerves, a sub-oesophageal ganglion, and a ventral 

 nerve cord, on which are situated ganglionic enlarge- 

 ments ; the antennary nerves are also thickened, 

 forming ganglionic rings. 



From an investigation of the nervous system of 

 Gydo2)s, Mr. Marcus M. Hartog, F.L.S., of Owen's 

 College, Manchester, has recently made out some 

 other points which he kindly allows me to insert 

 here. The most important of these are, that " gangli- 

 onic swellings are found near the terminations of all 

 sensory nerve fibres ; that the ventral nerve cord 

 gives off at the end of the third segment of the body 

 a pair of superficial cutaneous nerves, and at the 

 fourth segment two pairs, one to the rudimentary 

 fifth legs and another to two ventral muscles which 

 rise from the sternal portion of the fifth segment. 

 In the first abdominal segment is the fork described 

 by Claus and Leydig, but this takes its origin from 

 the superficial (ventral) aspect of the cord which is 

 continued onwards under the colleterial gland. After 



■i 



