152 
PACIFIC SCIENCE, Vol. II, July, 1948 
found to be more useful and more easily 
accomplished than chipping away the up¬ 
per layers of the carapace: With the for¬ 
ceps, grasp one of the dactyls about midway 
of its length and break it by bending it first 
to one side and then to the other. After 
breaking, exert an outward tug in an at¬ 
tempt to withdraw the broken distal half 
from the proximal portion. The withdrawn 
portion of the dactyl consists of the three 
upper strata; the fourth layer (membra¬ 
nous layer), if present, will remain attached 
to the proximal half of the dactyl because it 
is not closely adherent to the three upper 
strata now withdrawn. The sac formed by 
the internal membranous layer retains the 
form of the removed dactyl. Caution should 
be exercised in the operation to avoid de¬ 
stroying the membranous layer. Stage C 4 
is verified if the sac is present; if it appears 
absent, the stage is either C 3 or C 4 T. 
Stage C 4 T. Duration: From Stage C 4 until 
the death of the crab. In this stage the in¬ 
ternal membranous layer has become closely 
adherent to the principal layer and is not 
recognizable except upon histological ex¬ 
amination. 
This stage is common in most of the 
genera of larger Brachyura in which ecdysis 
occurs until the attainment of a certain 
maximum size; growth, therefore, ceases at 
this point. Its occurrence in P. crassipes 
seems substantiated by the evidence pre¬ 
sented herewith. MacGinitie (1937) de¬ 
scribed a specimen covered with barnacles 
and even small Mytilus edulis. He omits 
size data, but from a knowledge of the dur¬ 
ation of the early stages of the intermolt 
cycle this animal was probably in the C 4 T 
stage. On August 5, 1940, three large males 
of P. crassipes (44.2, 47.2, and 47.8 milli¬ 
meters in carapace breadth) were collected; 
each supported one specimen of Balanus 
glandula upon its carapace. One of the bar¬ 
nacles had a diameter of Va inch and the 
others were smaller. All three crabs were 
apparently in the C 4 T stage. Moreover, a 
large male in the C 4 stage (width, 47.6 mil¬ 
limeters) was collected on August 15,1940. 
Nearly 8 months later this crab was still 
in the C 4 stage with no evident signs of an 
impending molt. In field collections only 
one male over 44 millimeters in width was 
found in a stage later than C 4 , but many 
were designated as Q; likewise, no females 
over 40.0 millimeters in breadth were in a 
stage later than C 4 . The evidence would 
seem to insure the validity of this stage, but 
so few crabs are collected near the maxi¬ 
mum size that this stage must be generally 
uncommon and most crabs apparently die 
or are destroyed by predators, etc., before 
reaching a maximum size. 
Period D. Duration: 10 to 16 days; 21.0 per 
cent of the total interval. During this period 
the integument undergoes a series of transfor¬ 
mations preparatory to the impending molt, dur¬ 
ing the course of which the future spines are 
formed by the secretion of the epicuticular and 
pigmented layers of the new, developing integu¬ 
ment. The termination of this period is marked 
by resorption of the lime salts of the integument 
in both localized and generalized areas. At the 
onset of the period a diminution of activity, 
which is accentuated as ecdysis approaches, is 
apparent. There are four easily identified stages 
in this period: 
Stage D 4 . Duration: 3^2 to 6 days; 8.0 per 
cent of the total interval. This stage is 
marked by the formation of spines which 
are secreted several days before the initial 
chitinous stratum of the pigmented layer is 
deposited. When the dactyl is broken and 
examined, soft spines which push out the 
internal membranous layer overlying them 
can be observed. It is necessary to manipu¬ 
late the membranous sac to bring the spines 
into view, inasmuch as their extreme soft¬ 
ness causes them to be closely appressed to 
the surface of the sac. This character is the 
only clear-cut distinction between C 4 and 
