of protein synthesis. It would be possible to decide between these two possibilities by 

 determining the level of adenosine phosphates in the cell: if the block would occur in the 

 mechanism of oxidative phosphorylation or of respiration, the endergonic processes 

 {e. cr. protein synthesis) would continue to consume the ATP store of the cell imtill it sinks 

 to a certain low level. If, however, these endergonic processes would be blocked, ATP 

 would accumulate in the cell and the metabolism would be suppressed by lack of phosphate 

 acceptors. It should be possible to distinguish analytically between these two states. 



M. Lüscher (Switzerland). 1. To the question of Dr. Wigglesworth: What is the 

 influence of the C. allata vipon the determination of polymorphism in termites? Answer: 

 The С allata seem to play an important role in the determination of soldiers and supple- 

 mentary reproductives. The differentiation of white soldiers (jsre-soldier instar) results 

 from an activation of the С allata some time before ecdyson is being produced by the 

 thoracic gland. It seems that the differentiation takes place before the activity of the 

 thoracic gland and that the moult is delayed tmtil differentiation is completed, for if 

 moulting is induced artificially by injecting ecdyson 5 or 10 days after the implantation 

 of C. allata, intermediate forms between larvae and white soldiers are resulting. Supplemen- 

 tary reproductives are determined when a moult is released prematurely and when the 

 C. allata are activated after the activity of the thoracic gland.*) This follows from histo- 

 logical observations which show an enormous increase in volume of the C. allata just 

 before the moult. 



2. There is one question in which I am particularly interested and of which I should 

 like to hear other peoples opinion: the relation between the volume of a gland and its 

 activity. Many of us including ourselves are measuring the volmne of the C. allata in order 

 to get an indication of the state of activity of the gland. I do not belive that we are always 

 quite safe in doing so. In adult female Leucophaea the oxygen consumption is highest 

 at the time when the С allata grow most rapidly, but it is much lower when the volume 

 of the glands has reached its maximum. In last instar termite nymphs we do not find 

 significant differences in the volume of C. allata before an imaginai or before a regressive 

 moult, although we have to expect a difference in the secretion of juvenile hormone. 

 On the whole it is probably safe to state that a small gland is inactive and that a volumin- 

 ous gland is generally but not always active. 



H. J. Müller (DDR). 1. Im Zusammenhang mit Fragen der Photoperiode- und Cor- 

 pora allata-Wirkung möchte ich auf meine Untersuchungen an der Zikade Stenocranus 

 minutus F. hinweisen. Bei dieser Delphacide erfolgen Dotterbildung und Eiablage nur, 

 wenn sie nach oder auch während der Larvalentwicklung (die normalerweise imter Lang- 

 tag erfolgt) für 3 — 4 Wochen Kurztag (8/16) vmd danach wieder Langtag erhält. D. h. 

 weder unter Kurztag noch unter Langtag allein kann der gesamte Entwicklungszyklus 

 ablaufen. Es besteht ein Kurztagbedürfnis zum Anstoss der Oogenese, während zur Ei- 

 reifedann wieder Langtag herrschen muss. Auch wenn die Eiablage begonnen hat, kann 

 Kurztag zu gonotrophischer Dissoziation führen, die durch erneuten Langtag wieder 

 aufgehoben werden kann. Da die diapausierenden Weibchen viel Fett haben, imd 

 grösser sind, die diapausefreien aber, ohne an Fertilität und Vitalität einzubüssen, 

 kleiner und fettarm bleiben, scheint die Vorstelhmg gerechtfertigt, dass Langtag die 

 vegetativen Prozesse (Reservestoff- und Dotterbildung und Grössenwachstum), Kurztag 



*) Ligaturing experiments performed after the Symposium have shown that the C. allata are 

 not necessarj^ for the determination of supplementary reproductives. Their function in this case 

 is restricted to promoting yolk deposition in the ococytes. 



215 



