14 
PACIFIC SCIENCE, Vol. XVIII, January 1964 
Moreover, this activity occurred in the middle 
of the copulatory season when one would expect 
mating to occur. Thus it would seem that, like 
many mammals and other well-known animals, 
the males of this species of crab ( if no others ) 
become physiologically ready to copulate early 
in the season but are not aggressive until the 
female is ready. Such readiness is probably sig- 
naled to the male by some hormone which is 
released into the water as the last act of readi- 
ness prior to copulation. Thus, it is suggested 
that a hormone or some such chemical stimulus 
is secreted by the female which excites the male 
into action. This would answer the question of 
why the "eager” males did not simply grasp 
other females which were ever-present in the 
aquarium. Such a signal or trigger for copu- 
lation is not the same as that which begins 
oogenesis or spermatogenesis, but would only 
affect a male which had completed the matura- 
tion process. 
EGG DEPOSITION AND FERTILIZATION PE- 
RIOD: As with other crabs, fertilization occurs 
in this species at the time of ovulation and egg 
deposition. As the eggs pass down the oviducts, 
they become fertilized in the region of the 
spermatheca and then pass through the vulvae 
and are caught within the "egg basket.” The 
abdomen and the exopodites of the pleopods 
form the baskets and hold the eggs until they 
are firmly attached to the endopodites of the 
pleopods. Bimonthly counts of up to 300 fe- 
males of this species were made to determine the 
pattern of egg deposition and hatching. A few 
individuals begin egg deposition as early as 
February 18, but the percent of individuals 
(4.66-5.83) remains very low until about March 
10. At this time (see Fig. 4) there is an abrupt 
increase in the rate of egg deposition for all 
individuals. Egg deposition continues until about 
the first week in May, when over 90% of the 
individuals have eggs attached to the pleopods. 
According to Figure 4 it would appear that 
hatching begins very shortly after this peak is 
reached, for a gradual fall-off in the percent of 
individuals with eggs is noticed. It is quite 
possible that those individuals which produced 
eggs early in February may have begun the 
hatching process even prior to the peak of egg 
deposition. This may account for the fact that 
only 90% of the females are seen with eggs at 
any one time. When these data are compared 
with H. nudus, it will be seen that nearly 99% 
of the females may have eggs at one given 
time. As early as May 20 the second brood of 
eggs begins to appear for some individuals. 
Figure 4 shows a sharp increase in the number 
of females with new eggs, suggesting that only 
a short lag between broods occurs. A careful 
check of the condition of the developing em- 
bryos continues to show an increasingly large 
number of new eggs and a correspondingly 
smaller number of prehatch specimens. A cli- 
max of hatching for brood number one is 
reached shortly before the peak of egg deposi- 
tion for brood number two, which is around 
August 6. The percentage of females producing 
two broods drops to about 70% and shortly 
after the peak is reached hatching again occurs 
and continues until September 24, when less 
than 1% of the individuals still have eggs in 
the prehatch condition. 
To demonstrate more fully that a second 
brood is produced 38 females were dissected 
on June 13, shortly after brood number two had 
begun to appear. Of the 38, 22 had no eggs 
attached to the pleopods, while 16 had new eggs 
attached to the pleopods. Of the 22 specimens 
without eggs all but 6 had well-developed ova- 
ries that were visible through the membranous 
wall of the abdomen and upon dissection showed 
fully developed ova. Five of these 6 showed 
little or no development of ova within the 
ovaries while the sixth specimen proved to be 
immature and thus not ready for reproduction. 
Of the 16 individuals bearing new eggs none 
had well-developed ova in the ovaries, showing 
that these had now been spent on a second 
brood. Three of this latter group showed some 
very slight development in the ovaries in the 
way of pigmented eggs. It is suggested that these 
eggs simply were not ovulated at the time of 
deposition and hence remained to give the ap- 
pearance of slight development. 
On May 15 the number of females bearing 
their first brood of eggs reached 59% of all of 
the females observed. A special measurement of 
the 326 females collected was made to determine 
the relationship between size classes of those 
females with and without eggs. Gradations of 2 
mm from 8 mm to 20 mm were used so that 
crabs closely approaching one gradation or 
