Distribution, Food and reproductive Capacity of some fresh-water Amphipods, 21' 



10. Method of Moulting. 



A number of individuals, both adults and young, of all four species 

 were observed in the act of moulting. So far as could be determined 

 there was no difference in the process between adults and young nor 

 between the individuals of any two species. 



Fig. 4. Gammarus, moulting. 



Briefly stated the process took place as follows; — That part of 

 the exoskeleton covering the anterior part of the head, the antennae 

 and other cephalic appendages was the first to become loosened. A 

 fissure appeared between this portion and the first dorsal plate (fig. 4) 

 which gradually widened. The gnathopods were now used in such a 

 manner as to assist in pulling the skin over the head and away from 

 the appendages of the latter. However this skin remained permanently 

 attached by its mid postero-ventral marign to the remaining portion of 

 exoskeleton. Steady and deliberate wave like movements of the body 

 took place at intervals of about 8 or 10 seconds. The effect of these 

 was to cause a split on either side between the dorsal and coxal plates 

 which eventually extended from one half to two thirds of the distance 

 to the telson. As the movements continued, the first and second 

 gnathopods in turn were withdrawn followed by the first and some- 

 times the second peraeopods. A final and noticeably stronger wave like 

 movement resulted in the loosening of the posterior portion of the old 

 skin from which the amphipod now deliberately crawled. The whole 

 process took place normaly in from 7 to 10 minutes of which the 

 greater amount of time was required in the removal of the head piece 

 and that covering each gnathopod. 



One female Hyalella began to moult at 9,30 A. M. The skin split 

 normally, followed by the sliding off of the head piece and the with- 

 drawal of the gnathopods. The animal attempted to extricate the 

 peraepods but without success, for at 11,30 A.M., it was still struggling. 



