326 STEFAN KOPEC. 



sively females) were operated upon on the seventh day after their 

 last moult and lived under the same conditions of heat, light, and 

 humidity. We see that out of 25 brainless caterpillars only 5 

 underwent pupation, and in these the instant of beginning pupation 

 exhibits a certain retardation in comparison with the behavior of 

 the specimens used as a control. It is evident that the majority of 

 the brainless caterpillars did not undergo metamorphosis, remained 

 alive for weeks, and did not die until the whole store of fat in 

 their body had been completely exhausted. Large full-blooded 

 and fat caterpillars of 4-5 cm. in length become small during this 

 period, and were often scarcely I cm. long in their final state. At 

 the same time their bodies shrank and almost completely dried up, 

 their movements became fainter and fainter, until at last they died. 

 Caterpillars deprived of their brain do not, as a rule, die after the 

 operation as a result of any disease induced by the removal of the 

 brain, but, on the contrary, they live relatively very long. Only a 

 few specimens die soon after operation as a consequence of me- 

 chanical injuries taking place during the removal of the brain. 

 The essential difference between these insects and those used as a 

 control lies only in the fact that histolytical processes subsequently 

 followed by metamorphosis can begin only in animals the brain of 

 which has exerted a proper stimulus at the proper time. It is cer- 

 tain that the few brainless caterpillars which succeeded in becoming 

 pupae attained the stage only because the brain had already in- 

 fluenced the tissues before its removal. In this function, too, the 

 animals exhibit individual fluctuations ; here we evidently see speci- 

 mens in which the brain had begun to perform its stimulative part 

 very early, or had exerted it very quickly. It ought to be admitted 

 that, if we could succeed in feeding brainless specimens, their life 

 could be still longer. These caterpillars, however, would probably 

 not undergo metamorphosis. 



The opinion that the brain is of importance for metamorphosis 

 is supported by the following observations, which prove also that 

 the influence discussed sets in at a somewhat definite period, viz., 

 in females of Lymantria dispar L. in my breed between the seventh 

 and tenth day after their last moult. Let us observe the behavior 

 of the caterpillars which were deprived of their brain not on the 

 seventh day after the last moult as in investigations hitherto con- 



