194 
PACIFIC SCIENCE, Vol. II, July, 1948 
a length in excess of 4 millimeters were con¬ 
sidered nearly mature). A comparison of mature 
papillae and intermolt stages is indicated in 
Table 5. It is shown that papillae may closely 
approach maturity by the termination of stage 
C 3 , which fact, when combined with laboratory 
data, indicates that severance probably occurred 
at ecdysis or shortly thereafter. However, most 
do not attain maturity until stage C 4 is reached. 
The laboratory data likewise confirm this ob¬ 
servation. The diminished representation of 
mature papillae in period D is directly pro¬ 
portional to decreased frequency with which 
animals in period D are found in nature. 
TABLE 5 
Comparison between the Intermolt Stage 
and Frequency of Nearly Mature Papillae in 
Wild Specimens of P , crassipes . 
INTERMOLT 
STAGE 
NUMBER OF 
CRABS 
EXAMINED 
NUMBER OF 
NEARLY MATURE 
PAPILLAE 
c 3 .. 
33 
3 
G. 
96 
32 
Dx ... 
40 
13 
D 2 . 
27 
8 
Da . 
7 
2 
Total . 
203 
58 
The foregoing observations on regenerative 
progress and integumental synthesis have dis¬ 
closed some facts which not only effect a partial 
clarification of certain heretofore nebulous con¬ 
cepts of regeneration, but suggest new lines of 
approach toward the solution of pertinent prob¬ 
lems. These data indicate that within intermolt 
stage C 4 there is a critical period before which 
regeneration of a complete appendage will 
occur prior to the molt, and after which com¬ 
plete regeneration will not occur prior to the 
molt. Only one appendage of six severed dur¬ 
ing the C 4 stage in the captive animals com¬ 
pleted its regeneration before the molt, and 
this one was severed during a very early C 4 
stage. None of the five appendages severed 
during period D advanced beyond the blood- 
clot stage; whereas all of the 19 appendages 
severed in early intermolt stages underwent 
complete development; and those crabs which 
successfully underwent ecdysis had completely 
regenerated limbs. Stage C 4 , it will be recalled, 
marks the conclusion of the synthesis of the 
old integument, and all subsequent stages are 
concerned with its partial dissolution. It seems 
likely, therefore, that any regeneration which 
occurs prior to the complete synthesis of the 
old integument probably retards that synthesis 
until the regenerating member slackens its 
development in the latter stages. Meager sub¬ 
stantiation of this hypothesis was secured from 
crab No. 10, which, at the onset of regeneration, 
was in an early C 4 stage. Complete regeneration 
ensued prior to ecdysis, requiring 29 days from 
C 4 to D 4 —a longer period than that required 
by all other crabs in the experiment, although 
several were larger and would be expected to 
require even additional time if other conditions 
were equivalent. It seems reasonable to assume 
that experiments on regeneration may be 
performed with considerable accuracy if the 
investigator is cognizant of the transformations 
which occur during the intermolt cycle and is 
able to ascertain them without error. It is clear 
that the inability of former investigators to 
diagnose the intermolt period accurately has 
clouded the results of most of the experimental 
investigations on regeneration in decapod Crus¬ 
tacea. 
Measurements were made to ascertain the 
growth of the regenerating limbs on captive 
crabs for at least three successive molts. The 
graphic analyses of pereiopodal growth (Fig. 
17) indicate that three molts are undergone 
before regenerating limbs reach the size of the 
corresponding limb on the opposite side of the 
animal. After the first post-regenerative molt 
the limb extends to about three quarters of its 
normal size (PI. 2, Fig. 1). 
The probability of appendicular regeneration 
occurring from some point other than the 
fracture plane in P. crassipes was also investi¬ 
gated. Morgan (1902) demonstrated that this 
phenomenon could occur in hermit crabs, not 
only from points distal to the fracture plane 
but also from regions proximal to it. Although 
no controlled experimentation on P. crassipes 
