178 INVERTEBRATE PHYSIOLOGY 



trast with those of other investigators of crustacean molting. In the first 

 of these CarHsle found that eyestalk removal in Leandcr showed no evi- 

 dence of a molt-inhibiting hormone, and that the evidence pointed rather 

 to the existence of a molt-accelerating hormone in the eyestalk. In this 

 particular regard Carlisle seems to have overlooked Drach's (1944) study 

 with the same species, described earlier in this section. The conclusions of 

 these two investigators are diametrically opposed. An explanation for 

 these striking differences is not readily apparent ; Carlisle used only female 

 Leander, 55-70 mm. in total length (rostrum-telson), at a temperature of 

 13.5 ± 1°C, in nonrunning water, the animals being fed twice weekly, and 

 the average intermolt period being about 35 days ; Drach's experimental 

 and control animals (apparently) were of both sexes, were 25-50 mm. in 

 total length, were maintained at an average temperature of 14° C in the 

 month of October, were kept in running water, the animals were fed daily, 

 and the average intermolt period was about 20 days. Apart from the 

 possible difference of distribution between the two sexes among the ani- 

 mals used in the experiments of the two investigators, other differences 

 between the two studies may have been important ; Drach used smaller 

 animals than those used by Carlisle, and thus had predictably shorter 

 intermolt periods ; Carlisle apparently paid no attention to the stage of the 

 intermolt cycle in which the eyestalks of his animals were ablated, a factor 

 which Drach had shown was of considerable consequence in the subse- 

 quent molt ; for significant shortening of the intermolt period occurred 

 only if the eyestalks were ablated in stage C or in the first part of stage D^. 

 It can be seen from Drach's data that, in a population of 340 Leandcr of 

 the size class studied, only 60% were in these stages C and early D^ of the 

 intermolt cycle. An additional factor that might have contributed to these 

 differences may be an unrecognized artifact in the experimental conditions. 

 Scheer and Scheer (1954) observed no increase of molts in Leander after 

 eyestalk removal and interpreted ^heir results as suggesting a molt-accel- 

 erating factor in the eyestalks, similar to that proposed by Carlisle and 

 Dohrn. Carlisle ( 1954) found similarly that eyestalk removal in Carcinides 

 during the molting season gave no evidence of a molt-inhibiting hormone 

 from the eyestalks, when comparisons with control animals were m.ade. 

 Carlisle's observations and conclusions are at variance with those of other 

 investigators, but the resolution of these differences is not readily appar- 

 ent. Scheer (this symposium) has explained the difference in results be- 

 tween Drach's, Carlisle's, and his studies as possibly due to distinct races 

 of the Leander serratus studied (CarHsle, 1955). Most of the studies of 

 the effects of eyestalk removal on molting have been made on crabs and 

 crayfish ; the need for a wider exploration with other species of prawns 

 seems indicated to clarify this point. 



