Biology of Pacbygrapsus crassipes —HIATT 
147 
Since P. crassipes is available and easily col¬ 
lected along most of the west coast of the United 
States, and since it readily adapts itself to lab¬ 
oratory confinement, it will doubtless become an 
important experimental animal. Consequently, 
it would be advantageous in controlled experi¬ 
mental studies to know the precise intermolt 
condition of the animals employed. The chief 
objective in this study of the intermolt cycle 
was to ascertain the internal changes and to 
select some external morphological feature 
which would enable the worker to identify the 
internal or physiological condition. 
It is important to note that the changes dur¬ 
ing the intermolt cycle from its initiation to 
its termination do not differ with the size and 
age of the crab. The crab increases progressively 
in age throughout the intermolt cycle, and its 
completion is manifest by exuviation which is 
the result of an increase in size, but the physio¬ 
logical level at the onset of the following inter¬ 
molt cycle is exactly comparable to the like 
part of the preceding cycle. These transforma¬ 
tions, largely concealed during the intermolt 
cycle, are exhibited after ecdysis. Therefore, we 
may define the intermolt cycle as a series of 
transformations occurring during the period 
between the molts, not including the preceding 
or the impending molt. 
The literature relating to the intermolt cycle 
contains many expressions which designate vari¬ 
ous externally recognizable physiological con¬ 
ditions, such as "soft crab,” "hard crab,” "turgid 
crab,” and "limp crab.” All of these terms refer 
more or less directly to the amount of water 
or haemocoelic fluid contained in the tissues 
and haemocoelic spaces. Olmstead and Baum- 
berger (1923) were the first investigators to 
analyze scientifically these intermolt conditions. 
Early workers recognized a series of physio¬ 
logical changes for one or more periods within 
the intermolt cycle, but none considered the 
entire cycle representative of a continuous suc¬ 
cession of events. The search for knowledge 
relative to the formation of the integument led 
several investigators to discover isolated anato¬ 
mical and physiological phenomena with regard 
to the intermolt cycle. The most notable of 
these findings were (1) the discovery of the 
accumulation of calcareous reserves on the 
walls of the stomach; (2) the formation of 
setae; (3) the secretion of chitin. All of these 
phenomena were detected by Braun in 1875 
while studying the macruran, Astacus fluviatilis. 
Unfortunately, they were discovered in studies 
confined to stages immediately preceding the 
molt and no attention was directed to earlier 
transformation; hence he recognized no seria- 
tion. The meticulous investigations of Vitzou 
(1882), accomplished during observations on 
the histogenesis of the brachyuran integument, 
did not impress upon him that a seriation oc¬ 
curred during endysis. Paul and Sharp (1916) 
found the initial clue to seriation through bio¬ 
assays of the ratio of hepatopancreas weight to 
body weight in the crab, Cancer pagurus. Elm- 
hirst (1923) employed the traditional "pre¬ 
molt,” "post-molt,” and "intermolt” intervals. 
Later, Yonge (1932) discovered a series of 
stadia correlated with the amount of reserve 
calcium in the stomach walls of the lobster, 
Homarus gammarus, but this character is not 
available for use in studies on Brachyura, be¬ 
cause, with the exception of certain land crabs 
(Stebbing, 1893), nothing equivalent has been 
discovered in the Brachyura. Most of the seria¬ 
tion described prior to the studies of Olmstead 
and Baumberger (1923, 1928) is founded upon 
the interval of time elapsing after ecdysis. It is 
at once apparent that this method is restricted 
in utility because (1) it is inadequate for com¬ 
parative studies between species in view of the 
established interspecific differences with respect 
to the time lapse during the intermolt interval; 
(2) it is inapplicable for intraspecific com¬ 
parisons because the intermolt interval varies 
directly with age; (3) crabs reared under dis¬ 
similar environmental conditions show incon¬ 
sistent intermolt intervals. 
Olmstead and Baumberger, recognizing the 
need for a more accurate estimation of the 
