116 BULLETIN OF THE BUREAU OF FISHERIES. 
who stated that he had several times observed the process of copulation in the blue 
crab, told the author that the female crab voluntarily turns upon her back and spreads 
open the abdomen to expose the genital pores. Copulation lasts for a day or two, the 
female being carried about by the male, as before molting, except with the under side 
of her body uppermost. After copulation the female resumes her normal position and 
is usually carried by the male until her shell is hardened. 
Male reproductive organs.—Plate XIIX, figure 14, shows a view of the male crab 
with the abdomen turned back to display the intromittent or copulatory organs. It 
will be seen that there are no appendages of moment other than these upon the abdo- 
men. They correspond to the two anterior pairs of swimmerets upon the abdomen 
of the female and have been modified in the course of development to form copulatory 
organs. From Plate XLIX, figure 15, and Plate XLVIII, figure 2, it will be apparent that 
each organ consists of two parts, the one in front having a fairly broad base and being 
extended forward into a long, fine, slightly curved portion. The one in the rear is 
attached to the succeeding segment of the abdomen, is short, and has a sort of spur 
which fits into an opening in the base of the large anterior part of the organ. It evi- 
dently acts as a brace to strengthen the entire organ. 
Plate XLVIII, figure 11, represents a dissection of a male crab, showing the testes, 
which lie upon the digestive glands or ‘‘fat;”’ the glands, which secrete a pink-colored, 
jellylike fluid for carrying the spermatozoa; and the long, thin, white, convoluted 
tube, or vas deferens, through which the spermatozoa pass to the copulatory organs. 
Each of these tubes (Pl. XLIX, fig.15, and Pl. XLVIII, fig. 2), passes out through an open- 
ing on one of the segments, the coxopodite, of the swimming legs and into the base of 
the large part of the copulatory organ. The spermatozoa pass through a hollow in the 
center of these organs and into the sperm sacs of the female. 
Female reproductive organs.—Plate XLIX, figure 16, shows the under side of an 
adult female crab. The broad abdomen is turned back, exposing the openings of the 
two oviducts and the large swimmerets, which are borne on the lower side of the abdo- 
men. The copulatory organs of the male are inserted into the two openings during 
copulation. The eggs pass out through these openings when laid and become attached 
to the inner portion of each pair of swimmerets, thus forming the sponge (PI. L, fig. 19, 
and Pl. LI, fig. 22). 
Plate XLVIII, figure 3, represents the dissection of a female crab in the stage imme- 
diately preceding molting for the last time. The ovaries are very narrow and are 
white in color. After this molting and before copulation, the ovaries are very little 
larger, and the sperm receptacles are flat, empty sacs with a fairly tough, white wall. 
The ovaries are attached to the upper side of the sperm sacs, and at the point of attach- 
ment there is a passage leading from each ovary into the interior of the sperm sac. A 
tube or oviduct leads from each sperm sac and opens on the exterior, as shown in 
Plate XLIX, figure 16. At the time of copulation the pink, jellylike fluid carrying the 
spermatozoa is forced into the sperm sacs, which, as a consequence, become hard and 
distended and of a pink color (Pl. XLVIII, fig. 4, and Pl. L, fig. 17). The presence 
of sperm sacs of such a nature is always a sure indication that the female has mated 
within the preceding few days. 
