CH. VIII] FROGS, TOADS, AND NEWTS 281 



As soon as the weather has become sufficiently warm 

 the Frogs, which have hibernated some in holes and drain- 

 pipes, others in or on the mud at the bottom of ponds, 

 assemble in suitable bits of water and proceed to pair. 

 In this act the male mounts upon the back of the female 

 clasping her firmly round the pectoral girdle, just behind 

 the arm-pits, with his fore limbs. It is said that to 

 render the grasp more secure the modified digits, which 

 stand, after the fashion of a thumb, at an angle to the 

 others, are hooked over one another and further united by 

 .the mucus of the enlarged glands. This statement I 

 cannot confirm. I find that the two digits in question 

 are pressed firmly towards each other, nipping a piece of 

 the skin of the female between them. The protuberances 

 upon them are pressed strongly upwards against the body 

 of the female on either side of the sternum. It is possible 

 that their pressure may in some way assist in the passage 

 of ova into the oviducts. In this position the animals 

 remain for many days prior to oviposition. Eventually, 

 in the sunshine of early morning, the female discharges 

 the eggs into the water while the male pours sperma- 

 tozoa over them as they issue. 



Correlated with this use of the male index digit are 

 certain more deeply seated modifications which affect the 

 skeleton. The male second metacarpal bone is stronger 

 and broader than that of the female, and has upon its inner 

 side a projection for the insertion of the muscle (abductor 

 digiti II longus) which is employed in maintaining the two 

 front feet pressed together. .Similarly the lower half of the 

 humerus of the male bears upon its posterior surface a ridge 

 which reaches down to the inner condyle and is especially 



