8 THE HISTOET OF ANIMALS. [B. T. 



Some of these are furnished with a blow-hole, but have no 

 gills, as the dolphin and the whale. The dolphin has its 

 blow-hole on the back, the whale in its forehead; others 

 have open gills, as the selache, the galeus, 1 and the batus. 2 

 That is called the egg of the perfect foetus, from which the 

 future animal is produced, from a part at first, while the 

 remainder serves for its food. The worm is that from the 

 whole of which the future animal is produced, and the 

 foetus afterwards acquires parts and increases in size. 



2. Some viviparous animals are internally oviparous, as 

 the selache ; others are internally viviparous, as mankind 

 and the horse. In different animals the foetus assumes a 

 different form, when first brought into the world, and is 

 either a living creature, an egg, or a worm. The eggs of 

 some animals, as birds, are hard- shelled, and are of two 

 colours. Those of the selache and some other animals are 

 soft-skinned, and have only one colour. Some species of the 

 vermiform foetus are capable of motion, others are not. But 

 in another place, when we treat of generation, we will dwell 

 more accurately on these subjects. 



CHAPTEE V. 



1. SOME animals have feet, others have none ; of the for- 

 mer some have two feet, as mankind and birds only ; others 

 have four, as the lizard and the dog ; others, as the scolopen- 

 dra and bee, have many feet ; but all have their feet in pairs. 



2. And among apodous swimming animals some have 

 fins, as fish ; and of these some have two fins in the upper 

 and two in the lower part of their bodies, as the chryso- 

 phys 3 and labrax ; 4 others, which are very long and smooth, 

 have only two fins, as the eel and conger ; others have none 

 at all, as the lamprey and others, which live in the sea as 

 serpents do on land, and in like manner swim in moist places ; 

 and some of the genus selache, as those which are flat and 

 have tails, as the batos and trygon, have no fins ; these fish 

 swim by means of their flat surfaces ; but the batrachus 5 has 

 fins, and so have all those fish which are not very thin in pro- 

 portion to their width. 



3. But the animals which have apparent feet, as the cepha- 



' Squalus galeus. 2 Raia batos. 8 Spams auratus. 



4 Perca labi'ax. 5 Lophius piscatorius and also L. barbatus. 



