772 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [20] _ 
tuberances. The female is distinguished from the male, at the spawning 
season, by a character, which was recognized even in the time of Aris- 
totle: the last pair of walking legs, that is, the pair nearest the abdomen, 
presents near their distal extremities a spur, which is absent in the 
male, and the use of which will be revealed later. This animal is very 
common in the Mediterranean, but rare along the ocean coast except in 
the harbor of Brest. Like the lobster it is carnivorous and very vora- 
cious, consuming mollusks, worms, and fish, which are abundant upon 
the bottom in the waters where it lives. It rarely swims, or leaves the 
bottom, except to escape some threatened danger. 
The crab (Cancer) is distinguished by having a large, broad carapace, 
and its posterior pairs of legs all modified for walking; the anterior ‘pair 
is furnished with powerful pincers. The carapace is broader than long, 
and is denticulated, much like a saw, along the anterior border. The 
eyes are close together in front and furnished with short peduncles. 
The crab is partly terrestrial, partly marine; it inhabits holes among the 
rocks and in the sand, which are covered by the sea during every tide. 
It is carnivorous, its principal food being dead mollusks or any pieces of 
animal matter that may be within its reach. The most important edible 
species is the Cancer pagurus, which has the carapace smooth above and 
with the edges marked with prominent serrations. The rostrum is three- 
pointed and the large anterior feet are black and furnished with large, 
smooth tubercles upon the inside. This crab is very abundant in the 
ocean but rare in the Mediterranean. It grows quite large, and its flesh 
is, with reason, much esteemed, and must not be confounded with that 
of the common crab, about the only form found in our interior mar- 
kets, and which the fishermen of our coast consider of very little value. 
After this summary of three marine species which are useful as food 
to man, it is especially important that we should carefully study their 
mode of reproduction as well as the method of exercising this function, 
and the precise length of its duration, since by this means we shall be 
able to obtain a foundation for our efforts in artificial breeding. The pe- 
riod of reproduction with the lobster commences in October, with the 
rock-lobster in September, and it lasts about six months; but the union 
of the sexes takes place most commonly in November for the rock-lob- 
ster, and in December for the common lobster. -It does not end, how- 
ever, until towards the close of January. As with the cray-fish, the 
sexual act is accomplished belly to belly, and so closely and firmly do 
they clasp each other, that, if taken from the water at this period, it is 
with difficulty that they can be separated. With the rock-lobster the 
penis or copulating organ of the male does not penetrate into the body 
of the female, the seminal fluid being shed upon the plastron in the 
neighborhood of the external orifices of the oviducts, where it hardens, 
forming plates of a gelatinous consistency, from which the spermatozoa 
escape and work their way into the oviducts and thus to the ovaries, 
