STUDIES ON THE NECESSITY OF THE BRAIN FOR 

 THE INCEPTION OF INSECT METAMORPHOSIS. 



STEFAN KOPEC, 



GOVERNMENT INSTITUTE FOR AGRICULTURAL RESEARCH, PULAWY, POLAND.I 

 WITH 2 TABLES AND 4 FIGURES IN TEXT. 



CONTENTS. 



A. The influence of the brain on the inception of the metamorphotic 



processes 325 



B. The nature of the influence exerted by the brain on the course of 



metamorphosis 328 



C. The independence of the further processes of metamorphosis 333 



D. General conclusions and summary 338 



Gudernatsch ('12, '14) was the first to describe the acceleration 

 of metamorphosis in tadpoles fed on thyroid. These results were 

 confirmed for different amphibians by Laufberger ('13), Cotronei 

 ('14), Brendgen ('14), Abderhalden ('15, '19), Kaufman ('17, 

 '18), Kahn ('16), Hirschler ('iS-'ip), etc., and first of all by 

 Romeis ('i4-'i9). Adler ('16) ascertained that changes of tem- 

 perature of the environment cause changes of celerity of meta- 

 morphosis in tadpoles, together with simultaneous differences in 

 the structure of the thyroid. 



The results of the investigations of Loeb ('96) and Wintrebert 

 ('o5-'n), who cut the spinal cord or the nerves of larvae, contra- 

 dict the influence of the brain on metamorphosis of amphibians, or 

 at least the influence by means of nerves. On the other hand, 

 Babak ('05) examined the brain of the toad and came to the con- 

 clusion that the hind part of the brain affects metamorphosis, since, 

 when it is removed, the processes are arrested. He lays stress on 

 the fact that the removal of the brain effects the changes described 

 only in case the animal is operated upon before the first pair of 

 limbs have grown. Babak ('13) believes that here we have the 

 influence of hypophysis by means of chemical stimuli. Guder- 



i Paper from the Embryologico-Biological Laboratory, Jagellonian Univer- 

 sity, Cracow, Poland, presented in the Acad. of Sc., Cracow. Cf. Bull. Acad. 

 d. Sc. Cracovie, 1917. 



323 



