ZOOLOGY: J. LOEB 
315 
These experiments prove that the methods of artificial partheno- 
genesis can give rise to normal animals, even in forms so high in the 
scale as the frog; and that these animals are able to live and grow 
normally. 
The second problem connected with the raising of these frogs was to 
ascertain their sex. Loeb and Bancroft had investigated this problem 
5 
FIG. 2. 
three years ago on a frog and a tadpole four and a half months old.^ 
The investigation met with some difficulty owing to the fact that in 
young tadpoles and frogs both sexes have eggs in their sex glands. 
These eggs gradually disintegrate in the testicles, but at the age of 
four months eggs are still found in the gonads of those which will 
develop into males. This was the case in the gonads examined by Loeb 
