SEXUAL CHARACTERISTICS OF THELIA 535 
habitats. In his second paper he is very positive that the 
absence of the gonads has no effect upon the adult. Castrated 
males chirped as loud as ordinary males; their mating instincts 
were normal; they produced spermatophores, although no 
sperm was present to fill them, and the stridulating apparatus 
remained unchanged. Castrated females also had their normal 
structure and habits, and even bored in the ground with their 
ovipositors, although no eggs were present in their bodies. 
Regen’s work is the only one on paurometabolic insects. 
Turning again to the Lepidoptera, Kopeé has an interesting 
series of papers (’11, 713 a, 713 b), mainly on Lymantria dispar L. 
and Gastropacha quercifolia L. He developed a remarkable 
technique in the removal of the gonads, using a sickle-shaped 
hook and for the smallest larvae a hook of silver wire. For the 
transplantation of the gonads, he used sterile pipettes. Castra- 
tion and implantation of gonads of the opposite sex were per- 
formed on larvae of first, second, or third larval stage. Often 
he would repeat the ingrafting of gonads so that the abdomen 
and thorax of the operated individual would contain many in- 
stead of two gonads. Testes grafted into castrated females 
often grew to be larger than normal testes and in their histo- 
logical structure were normal. Ovaries which developed in the 
bodies of castrated males were always much smaller than normal 
ovaries. There were seldom more than one-fourth or one-fifth 
the normal number of ova developed and these were small. Sec- 
tions showed that their yolk granules were fewer and smaller 
than in normal eggs. In Gastropacha quercifolia, the ova 
developed in the male soma were yellow instead of green. The 
small size of the implanted ovaries, Kopeé maintains, is due 
entirely to lack of space for development in the male abdomen. 
The haemolymph or extract of triturated gonads, when injected 
into castrated individuals of the opposite sex, produced no 
effect upon the adult structures. In all his experiments (castra- 
tion, castration followed by implantation, and transfusion) 
the results are in perfect agreement with those of his predeces- 
sors and strengthen the idea that in insects the development of 
the secondary sexual characteristics is in no way dependent on 
