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 still farther 
from the Crustacean type than Chondracanthus. The Lernaeidae 
are vermiform, with their mouth parts forming a piercing 
and sucking tube. J. branchialis is found on the Cod. The 
Lernaeopodidae have their maxillipedes 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. 
OrpEeR 4. CIRRHIPEDIA. 
CHARACTERISTICS.—/ixed Crustacea whose body is enclosed in a 
fold of the skin, which is generally strengthened by calcareous 
valves. The body is indistinctly segmented. There are usually 
six pairs of thoracic feet, and the abdomen is rudimentary. 
Hermaphrodite, with mobile spermatozoa. Hxclusively marine. 
The class Cirrhipedia may be divided into five orders : 
1. Thoracica. 
. Ascothoracica. 
. Abdominalia. 
Apoda. 
. Rhizocephala. 
Ot H Oo bo 
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 
