the active principles present in the postcerebral glands. During the London Congress 

 of last year Professor Gersch gave a lecture on neiiro-hormones isolated from the corjjus 

 allatum and the corpus cardiacum, and I wonder if Professor Gersch has realized that 

 the Scharrers have ahvays kept the process of neuro -secretion separated from other 

 neuro -humoral activities. Although I can follow as a physiologist Professor Gersch, 

 when he prefers to collect all hormones secreted by the nervous system under the name 

 "neuro-hormones", I think he must be very sure, however, that the nervous system 

 is involved. To mj^ idea, the products found in the corpus allatum may not be named 

 as such. The corjDus allatum is of epitheliar origin and not, as the corpus cardiacum, 

 of neural origin. I wonder whether Professor Gersch has realized this and what reasons 

 he has for this opinion. 



Professor C. M. Williams succeeded in extracting from the abdomen of the male 

 Cecropia silkworm a substance which sujDpresses the formation of adult characters in moul- 

 ting pupae of this species. The similar activity has been found in the vertebrate Thymus, 

 in beef tenderloin and in cream. We have only experience with the male Cecropia 

 abdominal extracts. In my experiments, this extract increases oxygen consumption 

 in the Colorado Beetle homogenates, but after injection in allatectomized females 

 it does not produce a state of reproduction and activity. Injected in Colorado Beetle 

 pupae it provides metathetelic effects in the adults but thus not so in LocMsto nymphs. 

 In the experiment of Schoonhoven, a prolongation of diapause in Bupalus was caused 

 by this injection. I hope, therefore, that Professor Wigglesworth will agree in discus- 

 sing with us whether or not this hormone extract only mimics certain effects of the corpus 

 allatum without being identical with the "juvenile hormone". (This may of course be 

 several hormones). 



V. B. Wigglesworth (Great Britain). With regard of Professor De Wilde's sug- 

 gestion that the substances with juvenile hormone activity, which can be extracted 

 from mammalian and other sources, are not identical with the corpus allatum hormone 

 of insects; that, of course, cannot be decided imtil the chemical structure of these active 

 substances has been elucidated. It has long been realised that the juvenile hormone in 

 insects is merely controlling the manifestation of certain genetically determined characters 

 in the growing epidermal cells. It would be by no means impossible for a variety of che- 

 mical substances to exert such an effect ^ just as a wide variety of chemicals can exert 

 an "anti-bar" effect in bareyed mutants of Drosophila. It seems iinlikely that the active 

 extracts are merely stimulating the corpus allatum of the host insect to secrete juvenile 

 hormone, for they can have a strictly localized action confined to the point of application 

 in the epidermis. 



I fully agree with Dr. V. Kubista that the oxygen consumption of an insect is deter- 

 mined primarily by the energy demands of the body and not by the amounts of oxidative 

 enzymes present (Z wie ky and Wigglesworth, Proc. E. ent. Soc. Lond. {A)S1: 153—160, 

 195G). During growth and moulting it is highly probable that protein synthesis is one 

 of the most important processes which demand energy and therefore oxygen (Wiggles- 

 worth, Symp. Soc. Exp. Biol. 11: 203 — 227, 1957). But of course, a rising demand for 

 energy consumption will lead rapidly to a build-up of the necessary systems of respiratory 

 enzymes. 



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