204 
PACIFIC SCIENCE, Vol. II, July, 1948 
different years. Further, the evidence at hand 
shows with virtual certainty that some indi¬ 
viduals expel two batches of eggs within a single 
breeding season. The few crabs which mature 
a second batch of eggs near the close of the 
regular breeding season are probably the ani¬ 
mals which participate in the off-season spawn¬ 
ing during the winter months. 
Hatching and Subsequent Growth 
The multitude of empty egg capsules which 
adhere to each endopoditic seta of female exu¬ 
viae indicates that hatching occurs while the 
eggs are adherent to the female. Ovigerous 
females in the captive environment of the lab¬ 
oratory had plucked most of the sponge prior 
to complete embryonic development. At the 
termination of the normal incubation interval, 
the floor of the aquaria was often covered with 
loose, viable ova. Near hatching time the ex¬ 
ceedingly high mortality of these ova which 
had been removed by the female’s chelae seems 
to indicate that the movement of the abdomen 
and the setae by crabs in the wild environment 
may actually aid in the hatching process of the 
prezoea from the enveloping capsule. 
Hatching was observed microscopically. The 
investing membrane split about halfway around 
its periphery above the dorsal surface of the 
embryo; the prezoeae emerged dorsal side first 
in curled balls and soon began to move the 
appendages and to flex the abdomen. The pre¬ 
zoeae hatched in the laboratory were non- 
motile. Most of the prezoeae underwent ecdysis 
the first day; others molted during the second 
day. The first zoeae were likewise immotile, 
and no subsequent larval development was 
obtained because of inadequate facilities. For 
an account of the zoeal stages of closely allied 
species, the reader is referred to Hart (1935). 
The megalops stage of P. crassipes has been 
figured in outline fashion in Rathbun (1923, 
PI. 34, Figs. 1 and 2) and in Johnson and Snook 
(1935, Fig. 305), but an adequate description 
has heretofore not been published. On March 
8, 1941, several megalops of this species were 
collected at Carmel, California. Two of these 
were subsequently reared in the laboratory until 
the sixth crab stage, thereby definitely disclos¬ 
ing their identity. The collections were made 
by gently picking up rocks submerged in tide 
pools at a medium-high tide level (4.0 feet) 
and sweeping the surfaces with a soft brush 
while the rocks were submerged in a tub of 
sea water. Subsequently, the water was strained 
through a plankton net of coarse mesh. The 
transparency of specimens of the megalops 
stage makes it impractical to search for them 
on the rocks. The only clearly visible struc¬ 
tures are the few chromatophores and the gastric 
mill. The megalopa crawl and swim readily. 
Swimming is accomplished by rapid abdominal 
movements similar to those of many macrurous 
species. The dactyli are furnished with long 
hook-like spines to facilitate the grasping of 
rock and algal surfaces. 
The following account, together with a photo¬ 
graph of the megalops of P. crassipes (PL 2, 
Fig. 4), will fulfill the need for a description 
of this phase of the life history: length of cara¬ 
pace, 5.6 millimeters; width of carapace, 2.7 
millimeters; almost transparent, slightly yellow¬ 
ish in color; scattered black chromatophores on 
the eyestalks, on the carapace above the gastric 
region, and around the intestine; three chro¬ 
matophores on each merus of the ambulatory 
legs, two on each coxa, two on each propodus, 
and one on each dactyl; front wide, with center 
turned down to form the rostrum; chelae well 
developed; swimmerets broad and flattened with 
long plumose setae. 
The megalops of P. crassipes may be distin¬ 
guished from that of H. nudus and H. oregonen - 
sis by the greater size-—nearly twice as broad 
and long as H. nudus and twice or more as 
broad and long as H. oregonensis. In addition, 
H. oregonensis has no plumose setae on the 
smoothly rounded posterior margin of the telson, 
whereas P. crassipes has two long, median setae 
and several shorter ones. Setae similar to those 
described above for P. crassipes are found on the 
telson of H. nudus; therefore, distinction be¬ 
tween these two species must be made by size 
or by characters not mentioned here. 
