INSECT METAMORPHOSIS. 



interpretation of the hormonal role of the brain during insect 

 metamorphosis. Namely when grafting brains or other parts 

 of the nervous system on normal caterpillars of Deilephila 

 euphorbia this author did not observe any acceleration of meta- 

 morphosis. I cannot, however, consider as decisive experiments 

 like those of Gedroyc. in which the influence of grafted parts of 

 the nervous system are studied, the analogical parts of the host 

 not being removed. The introduced nervous tissue is present 

 here in excess and it might at most, but it need not elicit ac- 

 celerated metamorphosis, i.e., increase the effect of the function 

 which brain probably has when present in the organism in 

 normal quantities. 



I want to explain here a certain seeming contradiction between 

 the results of my former experiments, which has been justly 

 pointed to by the mentioned author. Gedroyc emphasizes that 

 from Table I. of my paper on the role of the brain in the meta- 

 morphosis of insects (cf. Kopec, '22) it follows that the control 

 caterpillars which fasted since the seventh day after their last 

 moult, and the head of which has been injured, the brain being 

 not removed undergo pupation simultaneously with the cater- 

 pillars which have not been operated upon at all, and which 

 were not deprived of food. On the contrary from my later 

 paper on the influence of starvation on the development of 

 insects (cf. Kopec, '24) it follows that caterpillars which have 

 been subjected to inanition since the seventh day after their last 

 moult undergo pupation later than the unstarved controls. 

 This discrepancy is however not essential for the caterpillars 

 subjected in either case to starvation the seventh day after their 

 last moult were not physiologically identical. In the second 

 case (Kopec, '24) they were normally fasting animals, in the 

 first (Kopec, '22) injured similarly to those the brain of which 

 has been removed. Owing to the severe injury, connected with 

 loss of blood, these caterpillars were not able to take food and 

 were therefore subjected indirectly to starvation. I have twice 

 just emphasized in connection with other experiments (Kopec, 

 '08 and 'n) that serious operations on caterpillars may have an 

 accelerating influence on the succeeding moult, which in the 

 above mentioned case corresponded to pupation. This acceler- 



