210 
PACIFIC SCIENCE, Vol. II, July, 1948 
cessive molts are required to bring a regenerat¬ 
ing limb back to normal size. With the excep¬ 
tion of the dactyl, regeneration from any point 
in the appendage other than the fracture plane 
has never been recorded in examinations of 
the several thousand crabs observed. Easy self- 
mutilation, rapid regeneration, and compara¬ 
tively brief intermolt cycles apparently con¬ 
tribute greatly to the success of this species in 
reaching and establishing itself in an area rich 
in food materials, notwithstanding the fact 
that it is exposed to constant predation. 
14. Predaceous enemies include gulls, rats, 
man, sea anemones, and, because of their canni¬ 
balistic tendencies, the crabs themselves. Exter¬ 
nal parasites on this species are a rarity. 
15. The usual brachyuran sexual dimorphism 
is present and the sexes appear in virtually 
equal numbers. Females were found to mature 
in 11 or 12 months, at which time they had a 
carapace breadth of about 15 millimeters. Male 
crabs are more precocious; mature males appear 
about 7 months subsequent to hatching, at 
which time they measure about 12 millimeters 
in carapace breadth. 
16. Copulation and impregnation are de¬ 
scribed in detail. Most of the adult females 
become ovigerous between April and Septem¬ 
ber; however, a few expel eggs during the 
winter months. Evidence seems conclusive that 
a portion of the females extrude two batches 
of eggs within a single breeding season. The 
incubation period requires approximately 1 
month. The gross development of the incubat¬ 
ing larvae and the behavior of the berried 
females are described. 
17. The megalops stage of P. erassipes is 
described and compared with other closely asso¬ 
ciated grapsoid species. 
18. An account of the growth of two care¬ 
fully reared crabs from the megalops to the 
sixth crab stage shows considerable individual 
variation in growth and a remarkable constancy 
with respect to total elapsed time between the 
post-megalopal molt and the attainment of the 
sixth crab stage. 
19. Morphological, physiological, and be¬ 
havioristic adaptations exhibited by this species 
disclose that it has made progress toward the 
attainment of a true terrestrial habitat, because 
the main prerequisites (aerial respiration, water 
conservation, swiftness, and homeostasis) have 
been partially achieved. Further, these adapta¬ 
tions—osmo-regulation in particular—seem to 
indicate that the apparently open path from 
the ocean to a terrestrial habitat via the inter¬ 
tidal zone is being traversed. 
REFERENCES 
Alcock, A. 1892. On the habits of Gelasimus 
annulipes. Ann. Nat. Hist. VI, 10: 415. 
-- 1899. Materials for a carcinological 
fauna of India, No. 4. Asiatic Soc. Bengal, 
Jour, and Proc. 68: 1-104. 
-- 1900. Materials for a carcinological 
fauna of India, No. 6. Asiatic Soc. Bengal, 
Jour, and Proc. 69: 279-486. 
Allee, W. C. 1926. Studies in animal aggre¬ 
gations; causes and effects of bunching in land 
isopods. Jour. Expt. Zool. 45: 225-277. 
-- 1938. The social life of animals. 293 p. 
W. W. Norton Co., New York. 
Andrews, C. W. 1909. On the robber crab 
(Birgus latro ). Zool. Soc. London, Proc. 
1909: 887-889. 
Baker, C. F. 1912. Notes on the Crustacea of 
Laguna Beach. Laguna Mar. Lab., Rpt. 
1: 100-117. [Pomona College Pub.] 
Barrell, J. 1916. Influence of climates on ver¬ 
tebrates. Geol. Soc. Amer., Bui. 27: 40-41, 
387-436. 
Bateson, W. 1889. Senses and habits of Crus¬ 
tacea. Mar. Biol. Assoc., Jour. 1: 211-214. 
Bethe, A. 1896. Ein Beitrag zur Kenntnis des 
peripheren Nervensystems von Astacus flu- 
viatilis. Anat. Anz. 12: 31-34. 
- 1897. Das Nervensystem von Carcinus 
maenas. Arch. f. Mikros. Anat. 50: 460-546, 
589-640. 
Boone, L. 1927. The littoral crustacean fauna 
of the Galapagos Islands. Part I, Brachyura. 
Zoologica 8: 127-288. 
Braun, M. 1875. Ueber die histologischen 
Vorgange bei der Hautung von Astacus flu - 
viatilis. Arb. Inst. Wurzburg 2: 121-166. 
Brock, V. E. 1943. Contribution to the biology 
of the albacore ( Germo alalunga) of the 
Oregon coast and other parts of the North 
Pacific. Stanford Ichthy. Bui. 2(7): 199-248. 
