338 STEFAN KOPEC. 



quently on the removal of separate parts of the nervous system. 

 A proof of this is that they also appear and in the same number 

 of cases in the specimens with intact nervous system used as a 

 standard and injured similarly as in the operations on the ganglia. 

 Therefore I consider it superfluous to describe these anomalies 

 here. 



D. GENERAL CONCLUSIONS AND SUMMARY. 



From the whole of this paper it follows that my results relative 

 to the influence of the nervous system on metamorphosis in insects 

 show a very great resemblance to the relations observed in am- 

 phibians. According to recent investigations (above mentioned), 

 iodin stored by the thyroid glands in amphibians is the direct 

 cause which elicits metamorphosis, but the production of this sub- 

 stance probably depends on the function of the hypophysis. Con- 

 sequently in both classes of animals metamorphosis would be con- 

 trolled by the brain, or part of it. In recent years experiments 

 have been performed on the influence of food containing thyroid 

 or hypophysis on the development of the larv^ of insects, but the 

 results of these researches do not as yet furnish an adequate mate- 

 rial for any conclusions. Abderhalden ('19) observed that a part 

 of the moths obtained from caterpillars fed on hypophysis was 

 very large ; many specimens from caterpillars fed on thyroid, on 

 the contrary, were very small. These data refer, however, to 

 phenomena of growth, and are possibly quite unrelated to the 

 problem of the rate of transformation here now discussed. Romeis 

 and v. Dobkiewicz ('20) studied the rate of development in larvae 

 of Calliphora fed on thyroid and obtained no distinct changes which 

 might have been attributed exclusively to the specific effect of the 

 thyroid gland. As I mentioned above, negative results of feeding 

 experiments with hypothetical specific influence ought not to be 

 considered as decisive, because it may be inferred from them only 

 that the substance used does not exert any effect on the organism 

 when given per os. Hanko ('12), on the other hand, ascer- 

 tained a very considerable influence of hypophysis on rate of moults 

 in Asellus aquaticus. But, as moults in Crustacea are not to be 

 totally identified with moults in insects having complete meta- 

 morphosis, these results also have no great importance for our 



