Biology of Pachygrapsus crassipes- — Hi ATI 
203 
second sponge within a single breeding season 
is available for P. crassipes, certain circumstan¬ 
tial evidence is sufficiently significant to remove 
the occurrence from doubtful rank. First, exam¬ 
inations were made of the ovarian development 
of berried crabs; and second, an examination 
of the ovarian development of recently molted 
female crabs, which might have been berried 
during the previous intermolt interval, was 
undertaken. Information on previous egg-bear¬ 
ing of recently molted females was secured 
through an examination of the endopoditic 
setae of the exuviae. The data concerning the 
ovarian development of ovigerous females are 
summarized in Table 10. 
The gravid ovaries of many berried females 
during the height of the breeding season con¬ 
tribute significant evidence to the support of 
the writer’s supposition that a second batch of 
eggs would be extruded within the 3 to 4 months 
remaining in the breeding season. However, 
it is to be noted that a few of the ovigerous 
females which, at the time of collection, had 
carried the expelled eggs about halfway through 
the incubation period exhibit very undeveloped 
ovaries. It is probable that these females would 
not extrude a second sponge in the time which 
remained in the spawning season. 
Nine females in stage A 2 and their exuviae 
were collected in June, 1941, for an examina¬ 
tion of their present ovarian development and 
of the endopoditic setae of the exuvia of each, 
to ascertain whether or not they had been ovi¬ 
gerous during the preceding intermolt interval. 
Only one had been ovigerous in the preceding 
intermolt interval and the ovary in this newly 
molted crab was ripe and gravid. Six of the 
others had small, undeveloped ovaries; two had 
ovaries which were nearly ripe, with ova of 
medium size. The outstanding feature of the 
data presented in Table 10, when associated 
with the data set forth immediately above, is 
the disclosure that an entire intermolt period 
may intervene between periods of sponge pro¬ 
duction. Inasmuch as the periods of ecdysis in 
this species are relatively frequent, it is not 
unreasonable that such a phenomenon should 
occur within the extensive breeding season. 
Exceptions to this behavior occur; e.g., it seems 
certain that the animal which contained the 
gravid ovary and which had a record of egg¬ 
bearing during the preceding intermolt interval 
would have become ovigerous for the second 
time in consecutive intermolt intervals. Whether 
or not the remaining crabs had been ovigerous 
earlier in the spawning season is conjectural. 
Some of the larger specimens probably had been; 
whereas the smaller individuals which con¬ 
tained, for the most part, relatively undeveloped 
ovaries probably would not have become gravid 
until the latter part of the spawning season. 
It seems probable, therefore, that the periodicity 
of gonadal development varies, not only between 
individuals, but within a single individual in 
TABLE 10 
The Size, Intermolt Stage, and Ovarian Development of Ovigerous Females of P. crassipes 
Collected during June, 1941. 
CARAPACE 
BREADTH 
(MM.) 
INTERMOLT 
STAGE 
CONDITION OF 
INCUBATING EGGS 
OVARIAN DEVELOPMENT 
27.0 
G 
eyes visible 
ripe, gravid 
32.4 
G 
yolky blastomeres 
ripe, gravid 
31.9 
G 
blastomeres to one side 
young, undeveloped 
26.7 
G 
highly differentiated 
ripe, gravid 
30.3 
G 
highly differentiated 
nearly ripe, gravid 
26.5 
G 
eyes visible 
ripe, gravid 
36.0 
G 
yolky blastomeres 
very young, undeveloped 
26.4 
G 
highly differentiated 
very young, undeveloped 
24.0 
G 
heart beating 
young, some development 
32.2 
G 
undifferentiated 
ripe, gravid 
