California Xanthidae — KNUDSEN 
9 
eggs in September, but no later record of egg 
bearing is available. The local Lophopanopeus 
and Paraxanthias remain in the normal tidal 
range, while ovigerous Cycloxanthops novem- 
dentatus migrate to about the minus 3- to 6-foot 
tide level before extruding their egg masses. 
Only one ovigerous female of this species has 
been deposited in the Hancock Foundation col- 
lection. Almost all of the ovigerous specimens 
collected by the writer were obtained by skin 
diving rather than by collecting on shore. Dur- 
ing the reproductive season the sex ratio at the 
higher tide levels is unbalanced, while in the 
winter and spring months there is an equal ratio 
of male and female crabs. 
Egg Mass 
The egg mass attached to the pleopods of the 
female varies in proportion to the size of the in- 
dividual and, to a lesser degree, between dif- 
ferent individuals of the same size-class. Table 
2 gives the estimated number of eggs carried 
by 15 xanthid crabs. In each case the eggs 
were stripped from the pleopods and 300 were 
counted. The volume of the 300 eggs divided 
into the total volume multiplied by 300 gave the 
approximate total number of eggs. In all cases 
the crabs used were smaller mature individuals 
rather than older and larger individuals. It can 
be seen that the total number of eggs is roughly 
proportional to the size of the individual. Ma- 
ture Lophopanopeus spp. would thus carry from 
1,000 to 6,400 eggs within their normal size- 
range, while an average-sized individual may 
carry around 3,500 eggs. An average Para- 
xanthias taylori may carry about 21,000 eggs and 
an average-sized female Cycloxanthops novem- 
dentatus about 45,000 eggs. 
Egg Extrusion and Attachment 
At the time of extrusion of the egg mass the 
individual eggs pass through the oviduct and 
into the spermathecae. Then they pass out of the 
body by means of the vulvae, and drop into a 
"basket” formed by the abdomen and its ap- 
pendages. The process of egg extrusion was ob- 
served on four occasions, but in each instance 
the eggs were aborted, and were not fastened to 
the pleopods. However, this process was essen- 
tially the same as when eggs are attached, except 
that the female crab periodically shook the eggs 
from her pleopods and allowed them to fall to 
the floor of the aquarium. 
During egg extrusion the female tilts her 
body backwards and elevates it above the sub- 
strate by extending her walking legs beneath 
her. The abdomen is lowered to about a 50 de- 
gree angle below the body plane. The sixth and 
seventh abdominal segments are turned upward, 
and together with their marginal "hair” serve 
to catch the eggs. The exopodites of the four 
pairs of pleopods are heavily set with "hair” on 
their anterior and posterior margins. When these 
are extended laterally they complete the "basket” 
which receives the eggs. Thus the basi-abdominal 
segments form the posterior wall, the median 
segments form the floor, the terminal segments 
form the anterior wall, and the exopodites form 
the lateral walls of the egg "basket.” Eggs stream 
from the vulvae and are received by the abdo- 
men. As they do so the endopodites of the pleo- 
pods move up and down through the loose egg 
mass. The endopodites are set with long smooth 
"hairs” to which the eggs are attached. When 
a part of an egg mass is examined microscop- 
ically it can be seen that there is an umbilical- 
like thread attached to each egg. This thread is 
wrapped around and attached to the pleopod 
"hairs.” However, the end of the thread is not at- 
tached to the "hairs” but remains free. One of 
the mysteries, still unsolved, is the origin of this 
thread, and the method of its attachment to the 
egg and to the pleopod "hair.” Broekhuysen 
(1936: 277) gives an excellent review of the 
literature, outlining nine possible answers to the 
problem, but concludes that the theories are still 
unsatisfactory for the Brachyura. The present 
writer observed that there is a sticky consistency 
to the entire egg mass shortly after being ex- 
truded, but he has not had opportunity to study 
this more fully. This sticky material may be a 
cement product secreted by the crab, as is the 
case of the lobster (Herrick, 1895: 48). How- 
Fig. 2. External genitalia: A, External genitalia of a male Cycloxanthops novemdentatus ; B, external gen- 
italia of a female Cycloxanthops novemdentatus. A, abdomen; I, intromittent organs; P, second pleopod in- 
serted into the first pleopod; P', pleopods to which the eggs are attached; V, vulvae. 
