222 METABOLIC HORMONES 



to decrease the permeability of the skin and of the excretory organs. 



In a dilute medium such as 50 per cent sea water, active transport 

 of ions is increased, gill permeability is decreased, and urine flow 

 is increased to about 24 per cent of the blood volume daily. At the 

 same time there is a limited swelling of the tissues (Webb, 1940). 

 The increased diuresis is presumably achieved by an increased 

 secretion of the diuretic hormone from the sinus gland causing 

 increased impermeability of the kidney tissues, as well as of the 

 gills. 



Carlisle (1956) has claimed that the diuretic hormone of 

 Carcinus differs from the moult-inhibiting hormone that is also 

 obtained from the eyestalk, because only in the winter, at least at 

 Plymouth, could he extract a moult-inhibiting substance, even 

 from the sinus glands of the same species ; extracts of sinus gland 

 from a number of other Crustacea were effective at all times of the 

 year in reducing water content. The diuretic extracts could not be 

 obtained from the cerebral ganglia, although these yield a strong 

 moult-inhibiting extract. Passano (1953) claims that the differ- 

 ences are quantitative and that the tissues have a lower threshold 

 value of sensitivity to the water-balance effect than to the moult- 

 inhibiting hormone. 



The observation that eyestalk removal reduced deaths of Carcinus 

 from exposure for 24 hr to conditions of lowered salinity (Knowles 

 and Carlisle, 1956) remains obscure. Survival would seem to 

 require the presence, rather than the absence, of the diuretic 

 hormone in the eyestalks. (Carlisle, in lit. 4.3.1957, agrees that the 

 situation is far from clear, and thinks that perhaps in Crustacea, as 

 in vertebrates, the balance of water, or of water and salts, is under 

 the control of two hormones. The moult-promoting hormone from 

 the Y-organ may be one of them.) 



Insecta. a diuretic hormone has been claimed for the beetle 

 larva, Afiisotarsus cupripenniSy and perhaps for other insects such 

 as Blaptica (Nunez, 1956). It appears to be secreted by the brain, 

 and is possibly stored in the corpora cardiaca, which were not 

 separated from the brain in the experiments. The larva lives in a 

 damp environment and can take up water by endosmosis through 

 the integumental cells lining the tracheoles ; but it normally remains 

 constant in size and weight by excreting the excess water into the 



