277 



ORDER XI. LERN^EIDA. 



815. The animals of this Order depart so widely from the 

 ordinary form of the Crustacea, that, until their early state was 

 known, they were ranked among the lower Articulata. In their 

 adult state, there is an almost complete absence of members or 

 appendages ; and those which remain are destitute of joints, 

 being merely fleshy lobes serving to attach the animal to 

 the surface of that on which it lives. They all bear a more or 

 less close resemblance to the Lerncea, an animal which is not 

 unfrequently found on the eyes and gills of Fish. The form of 

 the adult is displayed in Fig. 501 ; which 

 shows its long suctorial trunk or proboscis 

 (a) ; its short thorax (&), bearing the pair of 

 legs (c), by which the animal is attached; 

 its large abdomen (d), and its two egg- 

 capsules (0). The legs are united to each 

 other at their extremities ; and bear a kind 

 of sucker (/), which is applied to the surface 

 attacked by the animal, and assists in retain- 

 ing it there. The whole anterior part of the 

 body, however, is usually buried in the sub- 

 stance of the part, from the juices of which 

 the Lernasa derives its nutriment. However 

 dissimilar the form and characters of this 

 creature appear, to those of even 

 the preceding group, yet its con- 

 nection with them is made evident in two ways. 

 In the first place, there are numerous parasitic 

 species, which depart less from the ordinary type ; 

 forming a gradual transition from the Suctorial 

 Crustacea of the last order, to the highly-aberrant 

 FIG. 502.-LARVA f orm presented by the Lernsea ; so that, if the latter 

 is excluded, it would be difficult to say where the 

 line is to be drawn. And again, the early forms of the Lernaea 

 (Fig. 502) so strongly resemble those of the Cyclops and other 



FIG. 501 LERN^A. 



