ADAPTATION AND INHEEITANCE KAMMEREK. 433 



the time when the fore limbs are about to erupt, and all adaptations 

 to a terrestrial existence now appear emphasized. 



The fourth cycle of adaptation and inheritance. If one keeps 

 gravid midwife toads in a high temperature (of 25° to 30° C), then 

 they omit the brooding stages above described and return to the 

 primitive methods of reproduction peculiar to the rest of the toads 

 and frogs. The unusual heat forces the animals to seek coolness in 

 the water basin, which is at all times at their disposal. Here the sexes 

 meet and fertilization and oviposition take place. But the moment 

 the gelatine capsule of the egg comes in contact with the water, it 

 swells (fig. 9, detail fig. 4a) and loses its viscosity and therefore its 

 property to draw itself tightly about the thighs of the male later upon 

 drying. The male is therefore unable to fasten it to its posterior 

 extremities. The string of eggs therefore remains in the basin, in 

 which a few of them develop in spite of the changed conditions. 



In the same proportion in which the seeking of the water and the 

 completing of the reproductive processes without brooding become a 

 habit, so that the animals even without the stimulus of high tempera- 

 ture conduct themselves in this manner, do certain changes occur in 

 the eggs and larvae which correspond to a closer approach to the 

 original methods of reproduction of toads. The number of eggs and 

 their ability to develop in water becomes decidedly increased. The 

 aquatic eggs possess a lesser amount of yolk than the terrestrial eggs, 

 and are therefore smaller and different in color, but owing to their 

 swollen gelatine layer, they appear just as large as formerly. From 

 these eggs emerge larvae which belong to an earlier stage than those 

 normally produced, representing an intermediate stage between this 

 and that of the rest of the toads. They possess external gills, of 

 which the midwife toad has only a single pair (the anterior), (fig. 9, 

 detail fig. 46). Toads produced from such larvae are distinguished 

 from normally produced individuals by being considerably larger. 



In order to test the inheritance of these reproductive adaptations I 

 permitted aquatic eggs derived from animals which had become 

 accustomed to this mode of oviposition to develop under normal 

 conditions, in a room in which the control animals are kept and in 

 which these have kept normal. If the reproduction adaptation had 

 become a changed instinct, then the transmission left nothing to be 

 desired in the way of distinctness. The sexually matured young 

 midwife toads sought the water with the beginning of their iirst 

 reproductive period and deposited there their strings of numerous 

 small, dark-colored eggs without bestowing any additional attention 

 upon them. The aquatic eggs of later generations are still smaller 

 and possess still thicker investments, the additional gelatine being 

 obtained by a shortening of the spaces between the eggs in the string. 

 The larvae of later generations, derived from aquatic eggs (fig. 9, detail 



