PAIRING 85 



facilitating the pairing, when it has to take place 

 in the water. Our European Water-snakes pair on 

 land. 



During the rutting season a slight pressure on the 

 base of the male's tail may cause the protrusion of 

 the hemipenes, and so may a violent blow on the 

 spine of the reptile. Thus, recently killed specimens 

 of our Adder, with the organs everted, have more 

 than once been taken by the ignorant for snakes 

 with hind limbs, a mistake which must be pardoned 

 when we remember that male embryos of the slow- 

 worm and of snakes, in w r hich the hemipenes are 

 normally everted, have been described by zoologists, 

 who should have known better, as examples showing 

 external vestiges of limbs. 



The spermatozoa soon make their way up the 

 oviducts, in which the ripe ova have previously 

 descended, or which gradually descend shortly after, 

 these ducts becoming dilated in consequence. There 

 are usually more eggs in the right than in the left 

 oviduct, although the reverse has occasionally been 

 observed. 



Some snakes lay eggs shortly after impregnation, 

 or a few weeks later; in others the young undergo 

 their development within the oviducts, each envel- 

 oped in a thin, transparent, membranous capsule, 

 which is torn immediately before or immediately 

 after parturition, such species being termed " ovovi- 

 viparous." Just before oviposition the female curves 



