CRUSTACEAN METABOLISM 215 



suggests that the molt-inhibiting hormone is formed or active only before 

 this stage. 



Scudamore (1947) showed that eyestalk removal not only results in 

 precocious molting, but also increases oxygen consumption. Bauchau 

 (1948a) observed a similar increase in the crab Eriocheir sinensis, as 

 did Edwards (1950) in Ucapugilator and U. pugnax. Frost, Saloum, and 

 Kleinholz {\9Sl) ,\xs,\ng Astacus troivbridgi,'a.r\d^\\ss (1951, 1953), with 

 Gecarcinus lateralis, showed that sinus-gland removal has little or no 

 effect on oxygen consumption, whereas eyestalk removal is followed by an 

 increase. This result suggests that the factor active on oxygen consump- 

 tion, like that responsible for molt inhibition, is formed outside the sinus 

 gland, presumably in the X-organ, and merely stored in and liberated from 

 the sinus gland. Edwards ( 1950) reported that the diurnal cycle of oxygen 

 consumption in fiddler crabs ( Uca spp. ) is eliminated by eyestalk removal. 

 Brown, Bennett, and Webb ( 1954) found that the tidal rhythm, but not 

 the diurnal rhythm, is eliminated by this operation. 



It is tempting to consider that the molt-inhibiting factor and the factor 

 which inhibits oxygen consumption are identical. In this connection, it is of 

 interest that the Naples race of Leander serratus gives no evidence of a 

 molt-inhibiting hormone. We removed eyestalks from 114 animals in all 

 stages of the cycle, and observed no acceleration of molting or of any steps 

 leading to molting (Scheer and Scheer, 1954a). In these same animals, 

 eyestalk removal is without effect on oxygen consumption. The mean 

 value, corrected for body weight, for 25 normal animals was 14.50 /xl/hr. ; 

 that for 25 eyestalkless animals was 12.45 /xl/hr. ; the difference was not 

 statistically significant (Scheer and Scheer, 1954b). The Naples race 

 differs in its response to eyestalk removal from that at Roscoff, where 

 Drach ( 1944) found an increased frequency of molting following eyestalk 

 removal. The Plymouth race of Leander serratus, which is morphologically 

 distinguishable from that at Roscoff, behaves like the Naples race with 

 respect to the effect of eyestalk extirpation on molting (Carlisle, personal 

 communications). There is also the possibility that the effect of eyestalk 

 removal in increasing oxygen consumption is indirect, and results from 

 an increase in general motor activity. 



Growth and Nitrogen Metabolism 



The intermolt cycle is closely connected with processes of growth. Many 

 observers, beginning with Baumberger and Olmsted (1928), have noted 

 a distinct increase in size immediately after ecdysis. This increase results 

 primarily from the intake of water through the digestive tract (Baum- 

 berger and Olmsted, 1928; Drach, 1939). Removal of the eyestalks, in 

 those species in which this operation results in acceleration of molting. 



