G. В. Staal (Holland). In my work on Locusta it became evident that the effect 

 of J. H. and M. H. are opposite in many respects. Implantations of extra corpora allata 

 (C. A.) in young larvae may shorten the dxiration of larval instars, but increase the number, 

 implantations of extra ventral glands may increase the duration of instars but often 

 decrease the пшпЬег (by passing over the next morphologic larval stage). Although these 

 implantations may influence development also through changing the periods of availabi- 

 lity of the hormones diu-ing the moulting cycles, the evidence could also mean an import- 

 ant influence of a distinct hormonal balance or antagonism during normal development. 



In favour of this conception is also another fact: Sectioning of the nerves of the C. A. 

 in Und stage larvae as a rule leads to strong prothetely in the Vth stage (as a result 

 of delayed J. H. deficiency by arrest of growth of the C. A.). These individuals sometimes 

 resemble closely to Vth stage prothetelic larvae resulting from extra implantation of ventral 

 glands in the Und instar. 



On the other hand some phenomena rather seem to be influenced by absolute amounts 

 of each hormone. This is seen by implanting extra C. A. and ventral glands together 

 in Und stage larvae. These larvae may shown green colour (indicating exceess J. H.) 

 and passing over of the next morphologic stage at the same time after the next moult. 

 This may indicate an independent action of both hormones. 



To find a definite solution for these questions the described experiments should be 

 repeated with pvu-ified hormones in a more quantitative way. 



D. M. Steinberg (USSR). There is a well known fact that the presence of the hormone 

 of the corpora allata is inevitable for the process of ripening of eggs and accessory glands 

 in some insects. Without this hormone no normal process of development of the female 

 sexual glands and ripening occurs e.g.inDi^3tera as shown by E. Thomsen and J. Strang- 

 ways-Dixon or in Hemiptera as shown by A. S. Johanson. In some other groups 

 of insects, as in Phasmoidea or some Lepidoptera {Bombyx mori) the removing of the cor- 

 pora allata in neither larval nor pupal stage produces any effect on the egg production 

 in adult female. The immediate cause of these differences to the mentioned hormone 

 requirements has not been known so far. In think that the finding of the causes determin- 

 ing the différencies in the importance of the corpora allata hormone for egg formation 

 in different groups of insects deserves a profound comparative-physiological investigation. 



J. Strangways-Dixon (G. Britain). In some instances the volume of the corpus 

 allatum has been showTi not to be related to activity. However in other cases, this rela- 

 tionship appears to exist, but confusing results are still obtained. 



For instance. Dr. E. Thomsen (1949) and E. Thomsen and Hamburger (195.5) 

 demonstrated that corpus allatum activity induced an increase in oxygen uptake in Calli- 

 phora, but they could not show a relationship between oxygen consvimption and corpus 

 allatum volume. This suggests that corpus allatum volvune is not an indications of activity. 

 On the other hand, I have shown that corpus allatum volume fluctuates cyclically in Calli- 

 phora females,' that the cycles are a response to protein ingestion cycles and the corpus 

 allatum fluctuations induce carbohydrate ingestion cycles. In this example, corpus alla- 

 tum volume seems to be related to activity. 



In explanation of the conflicting results, it is suggested that corpus allatum volume 

 need bear no relation to blood hormone concentration. In Calliphora for instance a smaU 

 corpus aUatum might be an indication of low activity, but since the gland has been highly 

 active for several days before this stage, blood hormone concentration may be high. 

 In contrast, a large corpus allatum may be very active, but if inactivation is recent, 

 then the blood hormone concentration will be low. In this manner a corjDus allatum 



217 



