ARTHROPODA 271 



mandibles and both pairs of maxillae form claws. Behind 

 these are two pairs of bifid lobes representing the first two 

 pairs of feet. The abdomen is represented by a small papilla ; 

 just in front of this the oviducts open. The male is much 

 smaller than the female, and retains a much more definite 

 segmentation ; it is found clinging on to the female by means 

 of its antennary hooks in the neighbourhood of the opening of 

 the oviduct. It possesses an eye, and its caudal extremity 

 ends in two processes. Both male and female, like so 

 many other parasites, have very largely developed generative 

 organs. 



Many of the parasitic Copepods have departed stDl farther 

 from the Crustacean type than Chondracanihus. The Lernaeidae 

 are vermiform, with their mouth parts forming a piercing 

 and sucking tube. L. hranehialis is found on the Cod. The 

 Lernaeopodidae have their maxiUipedes enlarged, and in the 

 females united to form an organ of attachment to their host. 

 In this family the swimming -feet have entirely disappeared. 

 Some species are parasitic on Sharks and on the Salmon. 



Oedee 4. CIRRHIPEDIA. 



Characteristics. — Fixed Crustacea whose lody is enclosed in a 

 fold of the skin, which is generally strengthened ly calcareous 

 valves. The body is indistinctly segmented. There are usually 

 six pairs of thoracic feet, and the abdomen is rudimentary. 

 Hermaphrodite, with mobile spermatozoa. Exclusively marine. 

 The class Cirrhipedia may be divided into five orders : 



1. Thoracica. 



2. Ascothoracica. 



3. Abdominalia. 



4. Apoda. 



5. Rbizocephala. 



The last four of these orders are composed of parasitic 

 species, whose habits have involved considerable modifications 

 in their structure. 



The Thoracica include the common forms Zepas and Balanus 

 and many other genera, which have retained more of their 



