36 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



The male crayfish deposits its fertilizing matter in the form of sperniatophores upon the plates 

 of the tail-fan and upon the plastron of the female. The time of egg-laying varies from two to 

 forty-five days after copulation. When the time comes for the extrusion of the eggs, the female raises 

 herself upon her feet, and then the abdominal appendages secrete for a number of hours a grayish, 

 somewhat viscous mucus. She thereupon lies upon her back, bends her "tail" toward the opening 

 of the oviducts, so as to form a kind of cistern or chamber, as described by Lereboullet, into which 

 during the following night the eggs are received as fast as they are expelled from the genital organs. 

 This expulsion lasts from one to several hours. These eggs, which are always turned so as to present 

 their whitish spot or cicatricula uppermost, in order to be fertilized the more readily, are thus found 

 engulfed in the grayish mucus which fastens, in some degree, the swimmerets and the borders and 

 extremity of the "tail" to the thorax. This also helps to bound the pocket or chamber, in which there 

 is a certain amount of water inclosed with eggs aud mucus. Immediately after egg-laying we can 

 find in the water and mucus spermatozoids exactly like those contained in the spermatophores which 

 are attached to the plastron, and from which, in fact, the sperm-cells proceed. The spermatozoids are 

 thus in direct contact with the eggs and are in the presence of a vehicle which assists them to penetrate 

 the ova. Fecundation is effected in this chamber, that is, outside of the genital organs of the female. 



The spermatozoids found mixed with the eggs and mucus in the egg-chamber are like those 

 found in the spermatophores and male sexual organs. In the course of the first three days after 

 egg-laying these spermatozoids become spherical, pale, and continue immobile. After this they wither 

 and become smaller, darker, and more irregular. Finally, when, after the fixation of the eggs, the 

 excess of mucus has completely disappeared by means of pressure exerted by the incessant contractions 

 of the abdomen, which takes place in from six to eight days after egg-extrusion, those spermatophores 

 which still remain attached to the plastron consist of small white coriaceous filaments. The latter 

 are either isolated or composed of several adhering together. They have nothing to show but a 

 central cavity, in which the microscope can detect nothing but a few spermatozoids, more or less 

 withered. The wall of the spermatophores preserves its thickness and remains, as before, composed 

 of a hard, striated, tenacious mucus. 



On the lOtli of October a small species of Oambarus copulated in an aquarium, in 

 the following maimer: The animals lay on their sides, and the sternal surface of the 

 thorax of the male was pressed closely against that of the female. The abdomen of 

 the female was folded beneath that of the male. The male grasped with his great 

 claws the large pincers of the female, and thus held her securely, bringing also into 

 service the walking legs. According to Andrews (Johns Hopkins Univ. Oirc, vol. 

 xiv, p. 74), the spermatophores, which I did not observe, are deposited in the annulus 

 of the female, and the animals are firmly adherent by means of definite hooks and 

 ridges on the appendages of the male and female respectively. 



The following notes are interesting as showing how popular errors in regard to 

 the breeding habits of lobsters have arisen. Some of these statements, mixed with a 

 minimum of accurate observation, have been repeated so many times that they have 

 almost assumed the semblance of truth. 



Travis (191) writes to Thomas Pennant, in a letter on the habits of Homarus gam- 

 marus, published in 1777, that lobsters "begin to breed in the spring and continue 

 breeding most of the summer; they propagate more humano and are extremely prolific. 

 Dr. Baster says he counted 12,444 eggs under the tail, besides those that remained 

 in the body unprotruded. They deposit these eggs in the sand, where they are soon 

 hatched." This curious contradictory statement is repeated by Herbst (88), who says 

 that "they lay their eggs in the sand, where they are hatched by the sun." 1 



'The same notion existed in regard to the breeding habits of crabs. Thus, Herbst says: "The 

 sea crabs do not show so much care for their young as the crayfish. They try to deposit their eggs 

 either on the shore in the sand or they commit them to the sea, which washes these eggs thus extruded 

 in on the beach, where they are soon hatched by the sun, and the young seek again their proper 

 element." Of the laud crabs, he says : "They carry their eggs to the sea, where the females wash them 

 off from their tails. They are then cast up by the sea on the beach, where they are hatched by the sun." 



