3i6 A HISTORY OF FISHES 



of the middle layers of the oceans, sluggish in their movements 

 and soUtary in their habits, the chances of a mature fish finding 

 a mate of its own species might be somewhat slender. This 

 difficulty is overcome by the males, almost as soon as they are 

 hatched, seeking the females and each holding on to his selected 

 mate, and remaining attached to her body for the rest of his 

 life.* The site selected for attachment is quite haphazard, 

 sometimes being on the abdomen, sometimes on the sides or on 

 the head, or in the region of the gill-opening below the spine 

 on the pracoperculum : occasionally more than one male 

 becomes attached to a single female. Having gripped the 

 female with his mouth, the lips and tongue of the male apparently 

 unite with her skin, and the two become completely fused. 

 The mouth, jaws, teeth, fins, and gills of the tiny male — indeed, 

 almost all the organs except those connected with reproduction 

 — degenerate, and thereafter he is nourished by the blood of the 

 female (the two vascular systems being connected). 



* It has quite recently been suggested that the small Ceratioids without line 

 and bait, and with the eyes and nostrils enlarged {cf. p. 183), may be the free- 

 swimming males which have not yet become attached to females. 



