No. 493] 



NOTES AND LITERATURE 



if two kinds exist, arc injured or thai internal processes may lead 

 to the production of more functional sperm of one sex. These 



with the simplest possible apparatus ought to lead many natu- 

 ralists to repeat the experiment in different localities and with 

 different species. The only difficulty arises from the mortalily 

 of the tadpoles: for they must be kept until the time of meta- 

 morphosis (which, however, for the wood frog, the toad and for 

 some of the tree frogs takes place as early as .June of the same 

 year). By keeping the tadpoles in running' water, or by chan- 

 ging the water in the dishes every day. success is assured. 



at 



