CAMBARUS. 15 
. Peculiarities of the Young Stages of Cambarus.— The young Cambarus, like 
the young Astacus, when it leaves the egg is devoid of appendages on the 
first and sixth abdominal somites. The telson is not divided by a trans- 
verse suture. I have examined specimens of C. rusticus when but four milli- 
meters in length, evidently just released from the egg. They have much 
the same appearance as the embryo of Asfacus fiviatilis just before hatching, 
as figured by Rathke.* The cephalothorax is very large in proportion to the 
abdomen, and spherical ; the rostrum is bent down between the eyes; the 
antenn are laid back closely upon the breast. All of the appendages are 
soft, weak, and flexed beneath the sternum. There is no vestige of a gill on 
the last thoracic somite any more than in the adult Cambarus. The telson 
is a thick oval plate, entirely destitute of marginal seta, such as are seen 
fringing the telson in recently hatched young of Astacus figured by Huxley 
on page 220 of “ The Crayfish” ; agreeing in this respect with the telson 
of the embryo of Astacus as shown in Plate II. fig. 25, of Rathke’s memoir. 
I have no doubt that the newly hatched young of Astacus figured by Huxley 
has undergone one ecdysis since leaving the egg, whereby the embryonic 
cuticle has been discarded. 
Young specimens of C. Clarfi, seven millimeters long, taken from under 
the abdomen of the parent, have acquired the general form of the adult. 
The swimmerets, or posterior abdominal appendages, are well developed, 
while in the European Asfacus pallipes, ten days old and eleven millimeters 
in length, these appendages are enclosed within the notched telson, from 
which they are set free after the second or third moult, judging from speci- 
mens received from the Collége de France. Specimens of C. gracilis, nine 
millimeters long, and C. Bartonii, ten millimeters long, still under the pro- 
tection of the parent, have the swimmerets perfectly expanded, and even 
show the transverse suture of the telson. It seems probable, from a com- 
parison of these Cambari with the young of European Astaci, that the devel- 
opment of the former goes on inore rapidly after leaving the egg than that 
of the latter. 
It is interesting to observe that in the young C. Clarkii above mentioned 
the areola is moderately wide in the middle, where it is reduced to a line in 
the adult; the lateral spines of the rostrum are well developed, the acumen 
long and acute. In all the recently hatched Cambari which I have seen, the 
legs and claws are long and slender compared with the adult. 
* Untersuchungen tiber die Bildung und Entwickelung des Flusskrebses, Tab. I. fig. 16, Tab. II. fig. 25. 
