140 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



A specimen of a gray lobster (Astacus gammarus) was described at a meeting of 

 the Society Pkilomathique of Paris, on December 12, 1891, by M. Martin. It was 

 captured at St. Vaast-la-Hougue. in a trap with several perfectly normal lobsters. 

 The dorsal part of the carapace of the abnormal specimen was of a dark yellowish- 

 green color, with greenish-black spots. The green color disappeared rapidly on either 

 side of the dorsal median line, the yellow remaining, and passing into almost pure white 

 on the sides. There was not the least trace of marbling and none of the pronounced 

 blue color of the average lobster. The pleon was yellowish-green above, and yellow 

 on the sides. Large irregular spots of a deep bluish-black color ornamented each 

 segment, even in the dorsal parts, but without forming the usual marbled pattern. 



Martin rejects the hypothesis that this deficiency of color may be due to the 

 absence of light, supposing the lobster to have lived in a dark crevice in very deep 

 water, and regards this variation as adaptive, a conclusion which seems to me 

 gratuitous. He says, in a note, that M. Bietrix, of Concarneau, had a white lobster, 

 kept in a pond, which recovered its blue color at the next molt. A young male of 

 Al/pheus saulcyi, which I once kept for several days in an aquarium, molted and lost 

 completely the bright vermilion color of its claws. (94, p. 381.) 



Casual or temporary decoloration occurs in many species of Crustacea, as in Can- 

 cer pagarus, of which Malard (133) says that he has met with many cases of young 

 individuals living under stones in old oyster parks in the island of Tatihou, while the 

 permanent absence of pigment is characteristic of certain well-known burrowing 

 Crustacea which live in the sand, such as Hippa, Callianassa, and Gebia. It is doubtful 

 if the entire absence of pigment in such a form as Callianassa can be regarded as 

 adaptive; first, because the animal burrows, and is for the most part concealed; and 

 secondly, because its whiteness makes it a more conspicuous object on the sand than 

 it might otherwise be. This condition may, however, be the last term in a series of 

 changes, some of which were distinctly adaptive. 



VARIATIONS IN COLOR PATTERNS. 

 SPOTTED LOBSTERS. 



The spotted lobsters — "cabco," or "leopard lobsters," as they are variously called 

 by fishermen — exhibit an interesting and striking coloration, which is somewhat rare. 

 They appear to be occasionally captured, however, all along the coast. An experienced 

 fisherman at Rockland, Maine, said that he usually took one or two of this variety in 

 the course of the season. 



There is a well-preserved spotted lobster in the museum of the Peabody Academy 

 of Science, a female with hard shell, 11£ inches long. The whole upper part of the 

 body is of a light-yellow color, with purplish blue pigments (in the dried shell) so 

 arranged as to give a spotted or marbled appearance. The light- yellow spots on the 

 carapace vary much in size and shape, the largest being half an inch in diameter and 

 of a slightly irregular, rounded contour. The spots are confluent at the hinder end of 

 the carapace, where they form a marked yellowish area. On the sides of the carapace 

 the spots are small and tend to flow together. The "tail" is marbled above with 

 irregular yellow spots, in excess of the darker color. The tail-fan is yellow, beauti- 

 fully mottled with reddish-purple. The appendages are spotted in the same way, light 

 yellow predominating. The large claws are dark purplish-red above, with obscure 

 spots; but on the under side, they are of the usual bright reddish-orange color, 

 spattered with purple. 



