128 Frogs, and (heir Contributions to Science. 



with fanners that after their first appearance they must be 

 three times driven to their marshy beds by frost and i«-e 

 before the reign of winter ceases and that of gentle spring 

 begins. 



With the first warm days of spring, however, in this 

 latitude about the last of March, an upward impulse 

 seems to bring him from " the depths where he did lie" 

 and as the temperature of the water rises towards 60° his 

 activity and clamor increase. The blood, long stagnant, 

 courses with renewed activity, and desires, dormant for a 

 twelve month, awake to a new life. The little membra- 

 nous sacs we have spoken of vibrate unceasingly, pealing 

 forth what has been called "the tocsin of copulation." A 

 Frenchman once wrote and published a Memoir ou Les 

 Amours des Sauricns. A Frenchman alone is qualified to 

 describe the loves of the frogs. 



The male has no intromittent organ, and therefore im- 

 pregnation occurs without actual coitus. Establishing 

 himself on the back of the female with his arms clasped 

 firmly in a kind of tonic spasm about her body below the 

 scapulae, he resigns himself for a period of from fifteen to 

 thirty days to a seemingly passive enjoyment of his posi- 

 tion. The impregnation of the ova takes place after they 

 have left the female. In their passage forth they are 

 enveloped in a gelatinous covering, which absorbing water 

 makes an aggregate floating jelly-like mass many times 

 the size of the body from which it emanates. It is 

 commonly known by the name of frog spawn. Each 

 female lays from six to twelve hundred eggs, lays them 

 but once a year, and does not reproduce them after the 

 third or fourth year. 



The natural age to which the frog attains is not well 

 determined. It probably reaches from six to nine years. 

 The rana pipiena certainly lives much longer. JSoine 

 specimens that I have seen had all the marks of being 



