BOOK X. Lxxix. 165-LXXXI1. 169 



the small species. A swallow's first chieks are blind, 

 as are those of almost all species that have a com- 

 paratively large brood. 



LXXX. Unfertile eggs, which we have designated " wind-eggs. 

 wind-eggs, are conceived by the hen birds mating 

 together in a pretence of sexual intercom'se, or else 

 from dust, and not only by hen pigeons but also by 

 farmyard hens, parti*idges, peahens, geese and ducks. 

 But these eggs are sterile, and of smaller size and 

 less agreeable flavour, and more watery. Some 

 people think they are actually generated by the 

 wind, for which reason they are also called Zephyrs 

 eggs ; but wind-eggs are only produced in spring, 

 when the hens have left off sitting : another name 

 for them is addle-eggs. Wlien steeped in vinegar 

 eggs become so much softer that they can be passed 

 through rings. It pays best to keep them in bean 

 meal, or else chaff in winter and bran in summer ; 

 it is believed that keeping them in salt drains them 

 quite empty. 



LXXXI. The only viviparous creature that flies Thebat. 

 is the bat, which actually has membranes Uke wings ; 

 it is also the only flyer that nourishes its young with 

 milk, bringing them to its teats. It bears twins, 

 and flits about with its children in its arms, cariying 

 them with it. The bat is sviid to have a single hip- 

 bone. Gnats are its favourite fodder. 



LXXXII. On the other hand aniong land animals, Mcuingof 

 the snake is oviparous ; we have not yet described l"f^crocodiies. 

 this species. Snakes mate by embracing, inter- 

 twining so closely that they could be taken to be a 

 single animal with two heads. The male viper 

 inserts its head into the female viper's mouth, and 

 the female is so enraptured with pleasure that she 



399 



