RESULTS OF CASTRATION 69 



part, but that castration hindered the development of the 

 copulatory organs. Vandel considers this as a proof that the 

 gonads play an important part in the regeneration and 

 development of the copulatory apparatus in Planaria. 



Another experiment of Vandel (1922) is also of great interest. 

 As a rule the regenerating posterior fragment, containing in 

 the beginning the copulatory apparatus but no gonad, loses 

 the former by some process of remodelHng. In one case the 

 posterior fragment kept the copulatory apparatus and re- 

 generated to a perfect sexual individual. The histological 

 examination showed that a part of the testicle was left with the 

 posterior fragment. In some experiments Vandel destroyed 

 the gonads in the anterior fragments by exposing the latter 

 to a temperature of about 20° to 2i°C. Under these circum- 

 stances regeneration takes place, but no copulatory apparatus, 

 or an underdeveloped one, is to be found in the regenerated 

 animal. The objection might be made that both gonads and 

 the regenerating copulatory organs were simultaneously 

 inhibited by the action of the temperature. 



As the Planaria are hermaphrodite, the question arises as to 

 whether regeneration or persistence of the copulatory apparatus 

 is controlled by the testicle or by the ovary. To decide the 

 question, Vandel performed the following experiment. He 

 sectioned the animals in such a manner that from the anterior 

 fragment which contains the ovaries and the testicle, the 

 cephalic region with both ovaries was cut away. The frag- 

 ment regenerated in both directions; in the posterior part 

 the copulatory apparatus regenerated, as likewise happened 

 in the above-mentioned anterior fragments. Evidently the 

 ovaries are not necessary for the regeneration of the copulatory 

 apparatus. 



There seems to be some evidence as to the control of the 

 sexual apparatus by the gonad also in Mollusca. According 

 to Gould (1917; quoted from Vandel, 1922), there is in 

 Crepidula plana a very pronounced hermaphroditism. First 

 the testes and the male copulatory apparatus develop; after- 

 wards the testes and simultaneously the male copulatory ap- 

 paratus degenerate; and the ovaries and the female copula- 

 tory apparatus develop. Vandel thinks that there is evidence 

 that the development of the copulatory organs depends upon 

 the sexual glands. This is not true of all the organs, since the 



