INCEPTION OF INSECT METAMORPHOSIS. 325 



celeration or retardation, or whether it is completely arrested. The 

 problem was to find out a possibly well-defined center which would 

 have a more or less decisive influence on the time of inception or on 

 the rate of metamorphosis. Further, we must consider the means 

 by which this hypothetical influence could act on the processes of 

 metamorphosis. The mechanism of this influence ought to be 

 studied by means of special experiments, and the time at which the 

 influence begins to act ought to be found out. In order to answer 

 this question, I operated on female caterpillars of Lymantria dispar 

 L. after their last moult. Thus I was able to consider only the 

 processes of the pupation of caterpillars and the emergence of the 

 adult moths, without taking into consideration the processes of the 

 larval moult. 



It must be distinctly remarked that the whole material, experi- 

 mental as well as that used as a control, came from eggs of one 

 female only. All the caterpillars were reared in precisely identical 

 conditions. Moulting, pupation, and emergence of moths were 

 controlled every 12 hours; thus the error in determining the length 

 of life of caterpillars and chrysalids (see Tables I. and II.) could 

 not exceed 24 hours. 



As to the methods of removal of single ganglia, cf. operations in 

 my former paper (Kopec, '18). 



A. THE INFLUENCE OF THE BRAIN ON THE INCEPTION OF THE 

 PROCESSES OF METAMORPHOSIS. 



The behavior of caterpillars of Lymantria dispar L. deprived of 

 their brain (ganglion supra-cesophageale) allows us to draw the 

 conclusion that this ganglion has a quite specific quality, very im- 

 portant to the whole organism, and characterizing the brain as an 

 organ which excites histolytical processes in the caterpillar and 

 regulates the time of inception of the general processes of pupa- 

 tion. Let us consider the data given in Table L, which refer to 

 the pupation or to the death of caterpillars, whether normal, brain- 

 less, or those used as a control, viz., specimens which have been 

 injured in the same manner as the caterpillars deprived of their 

 brain, and which, in spite of the presence of the brain, refused food 

 as well as the brainless specimens. All these specimens (exclu- 



