NOTES ON THE LIFE HISTORY OF GAM:\IARUS CHEVREUXI. 553 



while growing as compared with the others, and finally some members 

 of a brood become sexually mature much earlier than others. It may 

 be simply that the weaklings lag behind, but as the male and female 

 differ so much in size at sexual maturity it may perhaps be a sexual 

 distinction. The results of our experiments may clear this point later. 



We have isolated 130 newly hatched young from different broods, 

 and are collecting and numbering the moults as they occur. We hope 

 when they attain sexual maturity to be able to trace back in the 

 moults the changes undergone, and the sexual distinctions if any. 

 Certainly the last moult before maturity shows sexual differentiation, 

 for the female already has the incubatory lamellae present, though 

 only partially developed, and the male has a few of the coiled sensory 

 hairs on the antennae, telson, etc. 



The time taken in the moulting of the young appears to be much 

 shorter than with the adult. For a few days previous they are less 

 active than usual, and a fiocculent sediment is noticed in the bottom of 

 the bowl. This, we think, is the secretion, probably lubricative, of 

 which a copious flow precedes ecdysis, oozing from between the terga, 

 and from all the joints of the antennae, the peraeopods, etc. Delia 

 Valle (1, p. Ill) refers to this in describing the moulting of the female. 

 Several young have been watched moulting ; they used their anterior 

 appendages in loosening the old cuticle of the head, but the whole 

 process, pulling off the head covering and slipping out of the posterior 

 portion of the cuticle, only occupied three or four seconds. 



The first moult seems to be the most critical ; in one brood fifteen 

 out of thirty-two died during the first moult. Afterwards the 

 mortality is comparatively small. Where the period between moults 

 has been longer than normal, the individual is undersized and evidently 

 weakly, in many cases not surviving the next ecdysis. Below are 

 tabulated side by side the rate at which two broods moulted, kept 

 under exactly the same conditions in the cold room. The right-hand 

 table refers to a brood seven days younger than the other, and it will 

 be seen that the rate of development was quicker in the younger 

 brood. Number d in Brood I was much larger than the others when 

 hatched, number k much smaller. This one did not grow perceptibly 

 after its second moult, and died seventeen days later in the effort to 

 moult again. Xumber c did not grow much after the second moult, 

 and died just after its fourth moult. Number i took the longest time 

 yet recorded for a third moult — twenty-six days ; it is an exceed- 

 ingly small specimen, and had great trouble in getting rid of the old 

 cuticle. 



