76 ANIMAL PARASITES AND MESSMATES. 



We may here remark that the change of ai^pearance 

 takes place only among the females ; the males preserve 

 their dress and their liberty. Some naturalists assert 

 that we must not accept the metamorphosis of either 

 sex as an established fact, except for the purpose of 

 arrangement. All, however, tends to show that Mons. 

 Hesse has fairly interpreted facts ; but it appears to us 

 probable that the whole of the history of these strange 

 crustaceans is not fully known. 



Fishermen have long since known whale-lice, the 

 Cyami of naturalists, of which we have already made 

 mention while speaking of free messmates. They live 

 at liberty on the skin of their host, and multiply with 

 extreme rapidity. These Cyami have a regular form, 

 but completely different from the others, and have given 

 (like the Eicini and the afore-mentioned crustaceans), 

 great trouble to systematic zoologists. The place which 

 they ought to occupy is far from being definitely fixed. 

 At all events they may be considered as a shorter kind 

 of Caprellse. 



As each whale has cirrhipedes which are peculiar to 

 itself, so each has its own cyami. Professor Liitken, of 

 Copenhagen, has made known ten or twelve species, all 

 found on cetacea, in the two hemispheres. The sup- 

 posed Cyamus, represented by Dr. Monedero as living 

 on the Biscayan whale, is a Pycnogonon. 



The Anilocrae and the Nerocilae, like the Cyami 

 and other genera, establish themselves on the back of a 

 fish which is a good swimmer. Jealous of their liberty, 

 they preserve their oars and their fins, in order to 

 change their convoy, when the desire seizes on them, 

 and do not imitate the Bopyrians, which instal them- 



