NATURAL HISTORY OF AMERICAN LOBSTER. 
301 
full and accurate account of the habits of the American crayfish during the breeding 
period has been given by Andrews.® 
Since the activities of the breeding crayfish are without doubt similar in some 
degree to those of the lobsters, and since they are at present far better known, I shall 
now give a summary of the instinctive acts and events in Cambarus for the period in 
question, drawn entirely from the work of Andrews referred to above. 
Pairing in Cambarus affinis takes place in spring (February-April) and fall (October- 
November). The male catches the female by the antennae or about the head, rolls her 
on her back, seizes her by the claws, stands over her body, and holds her in this position 
from 1 to 10 hours, during which time the sperm is transferred to the annulus or sperm 
receptacle on the ventral side of her thorax. This process may be repeated by “either 
male or female,” both of which are in hard shell. 
The male holds with his big forceps all the claw feet of the female in a bunch on 
either side, her abdomen being coiled under his, which closely presses it, he meantime 
supporting with his left or right fifth leg the abdominal appendages which are to transfer 
the sperm to the annulus*. The first two pairs of abdominal legs or modified pleopods 
of the male are directed downward and forward against the ventral surface of the thorax 
of the female. Since the pleopods tend to lie flat against the body, they thus fold or 
close upon the the fifth leg, which stops them, forming a rigid support, and at the same 
time giving them the necessary elevation. The male then presses close upon the female 
so that his pleopods are directed toward the annulus and are forced into it, where the 
sperm is deposited. Spines on the legs of the male further tend to hold the pair firmly 
interlocked. Cambarus affinis has a prominent spine on the third joint (ischium) of 
the third pair of chelipeds, which fits into the base of the fourth pair of legs of the female. 
Spines or hooks of this character are wanting in the lobster. Thus rigidly interlocked, 
the transfer of sperm goes on slowly and may last for hours. 
The vas deferens of the male is protruded or evaginated, as may be readily observed 
in all copulating males, forming a soft translucent double-walled tube, the lips of the 
opening being tightly closed. This evaginated duct fits in the groove which passes 
down the outer side of the first pleopod, and serves to conduct the sperm towards its 
tips. The appendages are rigid, sharp-pointed tools which are inserted into the 
annulus, and against which the modified second pair of pleopods are closely pressed. 
Sperm issues from the ducts as in the lobsters (compare fig. 2 , pi. xliv) in long vermicelli- 
like paekets, or gelatinous capsules known as spermatophores, and guided possibly by 
the second pair of pleopods, passes slowly down the groove of the first pair to the recep- 
tacle or chamber of the annulus. The female is remarkably passive and appears as if 
dead, while the excitement of the male is marked. 
While the spermatic receptacle of the lobster (pi. xxxm and fig. 4 and 6, pi. xliii) 
corresponds in function to the annulus of Cambarus, the latter appears to represent only 
the unpaired wedge-like middle piece of the former. The development of the seminal 
receptacle in the lobster proves that the middle piece in this animal is the anterior 
“Andrews, E. A. Breeding habits of the crayfish. American Naturalist, vol. xxxvm, p. 165-206, fig. 1-10. Boston, 1904. 
