The Pea-Crab

Abstract

(Pinnotheres pisum). THERE is an apparent discrepancy between Dr. J. H. Orton's interesting description of the pea-crab in NATURE of December 23, p. 533, and that given by Dr. W. T. Caiman, whom he quotes. Dr. Orton attributes the impunity with which the male crab and the male-like female sustain the nip of a bivalve to their “extraordinarily strong carapace” (p. 534). On the other hand, Dr. Caiman, discussing whether the Pinnotherid crabs should be reckoned commensals or parasites, observes that they “show one of the characteristics of parasites in being to some extent degenerate in their structure. The carapace and the rest of the exo-skeleton, no longer needed for protection, have become soft and membranous” (“Life of the Crustacea,” p. 217).