244 CRUSTACEA. 



of glands derived from the bean-shaped bodies above mentioned ; these glands, 

 whose efferent ducts open out at the base of the maxillipedes, yield a still' 

 secretion. Between these glandular bodies a dorsally-placed, pulsating organ 

 can be noticed ; this is probably a short, sac-like heart. A similar organ has 

 been observed in Tracheliastes by Vejdowsky, and in the larva of Lernaea 

 by Hesse. The rudiments of the genital organs are already clearly recognisable. 

 At the next moult the animal becomes sexually mature. The male does not 

 increase in size, but, in the female, the posterior region of the body becomes 

 very much enlarged. 



C. Branchiura. 



The Branchiura are. usually considered to be nearly related to 

 the Copepoda. This supposed relationship is based principally on 

 the similarity existing between the swimming limbs of Argulus and 

 those of the free-living Copepoda, and on the structure of the 

 mouth-parts-, which, according to the investigations of Claus, are 

 very like those of the parasitic Copepoda (Siphonostomata). Hook- 

 shaped mandibles and stylet -like maxillae can be distinguished. 

 These appear to be enclosed in a proboscis formed by the fused 

 upper and lower lips, together with lateral parts which must be 

 regarded as derived from the mandibles. These are followed by tw r o 

 pairs of maxillipedes which serve as adhering organs. The view 

 that these latter are the tw r o rami of the second maxilla which 

 have become independent receives special support from the position 

 of the ducts of the shell-gland, discovered by Claus on the basal 

 portion of the second maxillipede. Such a derivation of the maxilli- 

 pedes would constitute a fresh link between these forms and the 

 Copepoda. Argulus, indeed, shows in the structure of the genital 

 organs, as well as in other points of its organisation, some remark- 

 able peculiarities, and by the possession of paired, movable, lateral 

 eyes and of branched, hepatic tubes approaches the Phyllopoda, so 

 that we must probably consider the Branchiura as an offshoot from 

 the common ancestor of the Copepoda. 



The eggs, which are rich in food-yolk, and in which the germ-band 

 attains a ventral curvature, are attached by the female in row r s to 

 stones, etc. The young, when hatched (Claus), already greatly 

 resemble the adult in shape (Fig. 116), having the same body- 

 segmentation as well as the same number of limbs (apart from the 

 maxillae). 



The shield-like anterior portion of the body (cephalo-thorax) 

 consists of the cephalic segments fused with the most anterior limb- 

 bearing segment which carries a pair of swimming limbs. Three 

 five thoracic segments follow, each having a pair of swimming 



