104 THE HISTORY OP ANIMALS. [B. V. 



opposite : but the flat fish, with tails, as the batos, trygon, 

 and such like, not only approach each other, but the male 

 applies his abdomen to the back of the female, in all those 

 in which the thickness of the tail offers no impediment. 

 But the rhinse, and those which have a large tail, perform 

 the act by the friction of their abdomens against each other, 

 and some persons say that they have seen the male selache 

 united to the back of the female, like dogs. 



2. In all those that resemble the selache, the female is 

 larger than the male; and in nearly all fish the female is 

 larger than the male. The selache are those which have 

 been mentioned; and the bos, lamia, seetus, narce, batra- 

 chus, and all the galeode. All the selache have been fre- 

 quently observed to conduct themselves in this way. In all 

 viviparous creatures the act occupies a longer time than in 

 the oviparous. The dolphin and the cetacea also perform 

 the act in the same manner, for the male attaches himself to 

 the female for neither a very long, nor a very short time. 



3. The males of some of the fish which resemble the 

 selache differ from the females, in having two appendages 

 near the anus, which the females have not, as in the gale- 

 odea ; for these appendages exist in them all. Neither fish 

 nor any other apodal animal has testicles, but the males, 

 both of serpents and of fish, have two passages, which be- 

 come full of a seminal fluid at the season of coition ; and all 

 of them project a milky fluid. These passages unite in one, 

 as they do in birds ; for birds have two internal testes, and 

 so have all oviparous animals with feet. In the act of 

 coition this single passage passes to, and is extended upon 

 the pudendum and receptacle of the female. 



4. In viviparous animals with feet, the external passage 

 for the semen and the fluid excrement is the same : inter- 

 nally these passages are distinct, as I said before in descri- 

 bing the distinctive parts of animals. In animals which 

 have no bladder, the anus is externally united with the 

 passage of the semen, internally the passages are close 

 together ; and this is the same in both sexes : for none of 

 of them have a bladder, except the tortoise. The female of 

 this animal, though furnished with a bladder, has but one 

 passage ; but the tortoise is oviparous. 



5. The sexual intercourse/ of the oviparous fish is less evident, 



