74 AETRROPODA. 



In the mature state the eyes only retain a certain susceptibility 

 to light. The organs of hearing are two sac-like cavities situated 

 at the base of the first pair of cirri. 



The sexes are distinct in Ibla Cumingii and in Scalpellum 

 ornatum ; but many species of both genera are hermaphrodite, 

 notwithstanding which they have also a (supplemental) male 

 attached to them. 



Besides many species found on, or burrowing into, whales, fish, 

 mollusks, crabs, &c., one (Ornitkolepas australis, a larval form, 

 however) is said to attach itself to the feathers of a sea-bird 

 (Puffinus cinereus). 



There are about 100 species in this order. 



Ibla. 



Subclass II. EPIZOA. 



SUCTORIA. ICHTHYOPHTHIRA. 



Body elongate, subarticulate, the antennae and limbs termi- 

 nated either by suckers, hooks, or bristles. Mouth suctorial. No 

 respiratory organs. Females with external pendent ovisacs. 



The Epizoa are deformed and grotesque ectoparasites of fish 

 and other marine and freshwater animals. They differ from all 

 other Crustacea, except Cirripedia, Copepoda, and Podosomata, in 

 having no branchiae. They attach themselves to their prey either 

 by a suctorial mouth a conical tube resulting in a modifica- 

 tion of the upper and lower lips, accompanied by two bristle- 

 shaped pieces, the analogues of the mandibles or by a circular 

 disk formed upon the confluent extremities of the posterior pair 

 of feet. Another mode of adhesion is by certain processes that 

 grow from the head. 



