282 GENERAL CHARACTERS OF CIRRHOPODA. 



carefully removing the peduncle from its point of attachment, 

 the antennae may still be detected, even long after the animal 

 has acquired its mature form. In the interior of the recently 

 attached larva, the young Cirrhopod may be detected with its 

 valves and cirri ; the carapace and integuments of the larva 

 being thrown off subsequently. 



894. In the mature state, they correspond, as stated by 

 Mr. Darwin, to the anterior part of the body of the ordinary 

 Crustacea, the abdominal segments being almost always cast off 

 at the final metamorphosis. In the typical forms of the Order 

 the segments are six in number ; the mouth is prominent and 

 furnished with three pairs of appendages, some of which are in- 

 distinctly jointed ; the eyes are rudimentary*; the carapace is 

 represented by a series of shelly plates, and the limbs by jointed 

 cirri. Most of them are hermaphrodite, and when the sexes are 

 separate, the males are minute, imperfectly formed creatures, 

 which lead a sort of parasitic existence upon the surface of the 

 females ; whilst in a few hermaphrodite species, similar male 

 individuals (called "complementary males" by Mr. Darwin) are 

 found to exist. The eggs are discharged into the cavity of the 

 carapace, where they are retained until the exclusion of the 

 young larvaB. 



895. Mr. Darwin, in his admirable monograph of the Cirrho- 

 poda (published by the Ray Society in 1851 and 1853), from 

 which the material for the foregoing statements has been derived, 

 divides the sub-class into three orders, the Thoracica, the Abdo- 

 minalia, and the Apoda. As, however, the two latter groups 

 each contain only a single species, we have thought it unneces- 

 sary to follow him strictly in this respect). and it will be sufficient 

 for us to regard the Cirrhopods as forming an Order divisible 

 into three groups. These are : 



I. THORACICA, in which the body consists of six thoracic 

 segments, usually having six pairs of cirri, and inclosed in a 

 carapace formed of shelly plates. 



IE. ABDOMINALIA, with seven thoracic segments destitute of 

 limbs, and three abdominal segments bearing three pairs of cirri; 

 and with the body inclosed in a flask-shaped carapace. 



