THE YOUNG NATURALIST. 



169 



deep down in it. The interval between each moult varies according to the 

 time of year, and also differs in individual crabs. In summer time the 

 average is about five weeks. From October to April they do not generally 

 exuviate at all, and they bury themselves up in the sand at the bottom of the 

 aquarium at that time of year, and feed but seldom, in cloudy weather not at 

 all. They are three years or more attaining their full growth. How long 

 they live in the sea I do not know, but I have not been able to keep them 

 alive longer than five years. 



BRITISH FROGS AND TOADS. 



By LINNiEUS GREENING. 

 (A Paper read before the Warrington Field Club November 18th, 1887J 

 Continued from page 150. 



Ran a temporaeia (Common Frog.) 



In dealing with the life history of these Batrachians, we will start with 

 that of the common frog, which we will follow from the egg to the 

 adult. The number of eggs laid by one female is very large, ranging from 

 1,500 to over 2,000. I have counted the eggs of those which paired in a 

 state of nature, and those I paired in captivity, and I found the number of 

 eggs the same under natural as under artificial conditions. Judging by my 

 own observations, I should say the average is 2,000 ; the highest number I 

 ever counted was 2,500. The fertilization is effected as the eggs leave the 

 body of the female, there being no true sexual contact. The male, some 14 

 days before the laying takes place, has taken up his position on the back of 

 the female, clasping her firmly just behind and under her forelegs, and 

 assisted in retaining his hold by the suckers on his forelegs, pours out the 

 fertilizing fluid simultaneously with the laying of the eggs. As soon as the 

 eggs are deposited, the sexes separate, and do not breed again till the follow- 

 ing year, generally about the end of March. The newly laid mass of eggs 

 is as large as the body of the mother, and within an hour or so the mass has 

 increased tenfold. This remarkable increase in size is owing to the gelatinous 

 envelope of each egg becoming -distended by absorbed water, though even 

 after this increase the specific gravity of the mass is slightly greater than that 

 of water. It will not float but has sufficient cohesion to retain its cylindrical 

 form, when its base rests on the bottom of the pond ; hence in shallow water 

 it sometimes appears to be floating, though as a matter of fact it never does 

 so. It is curious to note that the embryos near the top of the mass, and 

 consequently in a warmer stratum of water, develop first ; their tadpoles 



