12 
thus are motivated in their feeding in a manner 
like that described by Hiatt for Pachygrapsus 
crassipes. 
On March 1, I960, the water temperature in 
the tanks at the Point Defiance laboratories 
reached the seasonal low of 6.9 C This low 
temperature was maintained for several days 
running and during this period almost all of the 
food offered to all species of crabs, including 
Hemigrapsus nudus and oregonensis, all three 
species of Cancer, and two species of Pugettia, 
was ignored. Probably this temperature marks 
a point at which the crab metabolism is retarded 
and little feeding is required or is possible. 
SYNOPSIS OF REPRODUCTIVE ACTIVITY: Fig- 
ure 4 shows that oogenesis within the ovaries 
begins sometime during the month of October 
and continues until the time of ovulation, fer- 
tilization, and egg deposition. Egg deposition 
begins about the middle of February and at 
about March 10 starts to increase rapidly. Egg 
deposition is completed at the end of April. In 
the early weeks of May hatching begins and 
continues until the end of July. The second 
brood appears very shortly after the hatching 
of the first brood begins, showing that there is 
a very short duration when the females are with- 
out eggs on the pleopods. Those females pro- 
ducing a second brood complete egg deposition 
by the first week of August and hatching is 
completed by September 24. At this time there 
is no sign of activity within the ovaries of the 
female and it is assumed that a period of quies- 
cence is resumed until oogenesis commences 
once again. 
OOGENESIS: Each month 10 to 12 females of 
this species were dissected and the ovaries were 
studied for signs of oogenesis. During October 
only one individual showed enough develop- 
ment that the ova could be measured (approxi- 
mately 0.23 mm). In November the specimens 
showed considerable size increment in that most 
of the ova were recognizable and measured 
slightly under 0.20 mm, though 2 of 14 indi- 
viduals showed ova slightly larger than 0.20 
mm. In January the ova averaged about 0.35 
X 0.29 mm. One individual out of 8 in this 
group showed ova only slightly larger than 
0.20 mm diameter. The February sample again 
showed a considerable increase in over-all size, 
with ova as large as 0.47 X 0.42 mm, but 
FIG. 4. The reproductive cycle of Hemigrapsus 
oregonensis . 
