408 COPE POD A. 



appendages. The two anterior pairs of swimming feet have the typical 

 structure, and consist of a protopodite bearing an unjointed exopodite and 

 endopodite. The first pair is attached to the cephalo-thorax and the 

 second (//) to the first free thoracic segment. The third pair is very- 

 small and attached to the second free segment. The mouth is situated 

 at the end of a kind of proboscis formed by prolongations of the upper 

 and lower lips. The alimentary tract is fairly simple, and the anus opens 

 between the caudal forks. 



Between this and the next known stage it is quite possible that one 

 or more may intervene. However this may be the larva in the next 

 stage observed (fig. 230 C) has already become parasitic in the mouth of 

 the Perch, and has acquired an elongated vermiform aspect. The body is 

 divided into two sections, an anterior vmsegmented, and a posterior formed 

 of five segments, of which the foremost is the first thoracic segment which 

 in the earlier stage was fused with the cephalo-thorax. The tail bears 

 a rudimentary fork between the prongs of which the anus opens. The 

 swimming feet have disappeared, so also has the eye and the spiral duct of 

 the embryonic frontal organ. The outer of the two divisions of the 

 maxilliped have undergone the most important modification, in that they 

 have become united at their ends, where they form an organ from which 

 an elongated rod (f) projects, and attaches the larva to the mouth or gills 

 of its host. The antennae and jaws have nearly acquired their adult form. 

 The nervous system consists of supra- and infra-oasophageal ganglia and 

 two lateral trunks given off from the latter. At this stage the males and 

 females can already be distinguished, not only by certain differences in the 

 rudimentary generative organs, but also by the fact that the outer branch of 

 the maxillipeds is much longer in the female than in the male, and projects 

 beyond the head. 



In the next ecdysis the adult condition is reached. The outer maxilli- 

 peds of the male (fig. 230 E, pm 2 ) separate again ; while in the female 

 (fig. 230 D) they remain fused and develop a sucker. The male is only 

 about one-fifth the length of the female. In both sexes the abdomen is 

 much reduced. 



In the genera Anchorella, Lernaeopoda, Brachiella and Hessia, Ed. van 

 Beneden (No. 506) has shewn that the embryo, although it passes through 

 a crypto-Nauplius stage in the egg, is when hatched already in the Cyclops 



stage. 



BrancMura. The peculiar parasite Argulus, the affinities of which 

 with the Copepoda have been demonstrated by Glaus (No. 511), is hatched 

 in a Cyclops stage, and has no Nauplius stage. At the time of hatching it 

 closely resembles the adult in general form. Its appendages are however 

 very nearly those of a typical larval Copepod. The body is composed of 

 a cephalo-thorax and free region behind this. The cephalo-thorax bears 

 on its under surface antennae (two pairs), mandibles, maxillipeds, and the 

 first pair of thoracic feet. 



The first pair of antennae is three-jointed, but the basal joint bears a 

 hook. The second pair is biramous, the inner ram us terminating in a hook. 

 The mandible is palped, but the palp is completely separated from the 

 cutting blade 1 . The maxilla would, according to Glaus, appear to be absent. 



1 It seems not impossible that the appendage regarded by Claus as the mandibular 

 palp may really-represent the maxilla, which would otherwise seem to be absent. This 



