Mar. 2 1, 1872] 



NATURE 



409 



many species of Cicindela, or tiger beetle. The common 

 English species, " C. campcsiris, frequents grassy banks, 

 and is of a beautiful green colour, while C. Jiiari/iina, 

 which is found only on sandy sea shores, is of a pale 

 bronzy yellow, so as to be almost invisible." He then 

 states that a great number of species found by himself in 

 the Malay Archipelago were similarly protected. " The 

 beautiful Cicindela gloriosa, of a deep velvety green 

 colour, was only taken upon wet mossy stones in the bed 

 of a mountain stream, where it was with difficulty detected. 

 A large brown species (C lieros) was found chiefly on dead 

 leaves in forest paths ; and one which was never seen ex- 

 cept on the wet mud of salt marshes, was of a glossy 

 olive so exactly the colour of the mud as only to be dis- 

 tinguished when the sun shone, by its shadow. Where 

 the sand beach was coralline and nearly white, I found 

 a very pale Cicindela; wherever it was volcanic and black, 

 a dark species of the same genus was sure to be met 

 with." 



But little attention has been given to adaptive colouring 

 among the lower invertebrate animals. Darwin, in his 

 last work on the " Descent of Man," calls attention to the 

 statements of Haeckel that the transparency of the Medusse 

 and other floating animals is protective, since their glass- 

 like appearance renders them invisible to their enemies, 

 though Wallace also alludes to this same feature (p. 258). 

 Mr. Edward Burgess informs me of a species of Acaleph, 

 Polyclonia frondosa, on the coast of Florida which lives in 

 the mud, and is brown in colour. Darwin, while admitting 

 that the transparency of these animals unquestionably 

 aids them to escape the notice of their enemies, yet doubts 

 whether the colour of rooUusks affords similar protection. 

 He says, " The colours do not appear in most cases to be 

 of any use as a protection ; they are probably the direct 

 result, as in the lower classes, of the nature of the tissues, 

 the patterns and sculpture of the shell depending on its 

 manner of growth" (vol. i. p. 316). 



In glancing over our New England Mollusca, however, 

 it seems that we do have very clear evidences of protective 

 adaptations among them, not only in their form, but more 

 particularly in their colour. It would seem strange indeed 

 if this were not so, since so many species of Mollusca form 

 an important portion of the food of many fishes,* and 

 also of certain species of birds. 



In a general way, we recall the sombre colours of the 

 shells of most species, varying through different shades 

 of yellow, brown, and green, in this respect resembling the 

 sand, mud, and rocks, or seaweed, in or upon which they 

 live, and we then recall by groups the land snails of our 

 woods, with their almost uniform brown tints, like the 

 dead leaves or rotten wood in which they live. 



The freshwater snails have similar shades to match 

 their peculiar habitats. 



The freshwater mussels, coloured likewise brown, green- 

 ish, or black, accord with their places of refuge. 



Among the marine forms we notice the adaptive coloura- 

 tion of certain species very well marked The common 

 Littorina oi\he coast swarms on the bladder weed, the 

 bulbous portions of which are olive brown in colour, or 

 yellowish, according to age. The shells of the Littorina 

 found upon it, present in their varieties these two colours, 

 and are limited to these colours, though now and then 

 delicately banded specimens are seen. 



Purpura lapillus, which generally hides beneath over- 

 hanging ledges, or is concealed under flat rocks, has gene- 



* Id an inlet near Salem the writer observed a school of i 

 along the bottom, and as they approached a certain point jumped right and 

 left in great alarm. For some time the disturbing cause could not be found. 

 On closer examination, however, a Cottus was seen to open his large mouth 

 and take in several of the little fishes. The Cottus was so perfectly protected 

 bv its colours that it was only recognised when the capacious mouth opened, 

 and only then were the minnows alarmed. Just beyond in their track was a 

 rusty tin fruit can, the little tin remaining on it reflecting the rays of the sun, 

 and from this harmless object they all turned affrightedly away. In this con- 

 nection it would be interesting to inquire into the food of fishes in respect to 

 their colours Those fishes feeding upon Mollusca would certainly not re- 

 quire that protection for concealment as those living upon more active prey. 



rally a dirty white shell, with, now and then, a specimen 

 bright yellow, or banded with brown. Wc are not aware 

 of any fish that feeds upon this species, though in the 

 almost universal white colour of the species an adaptive 

 colour may be secured in resembling the white barnacles 

 which oftentimes whiten the rocks by their nuinbers. 



In pools left at low tide where the rocks are often 

 clothed with the red calcareous alg;e we find the little red 

 Chiton. Certain Af^tili are green. The young of the 

 large M. modiolus has a rough coat of epidermal filaments, 

 looking like the aborescent growth of seme Alga or 

 Hydroid. 



The few species common to the mud flats exposed by 

 the retreating tide are coloured black or dark olive. 

 Ilyanassa obsoleta has the shell black, while the soft parts 

 are quite dark. A related form, Nassa triviliata, lives in 

 more sandy places, and has a similarly coloured shell. 

 Rissoa niinuta, inhabiting mud flats, has a shell dark 

 olive, or nearly black, while other species of Rissoa are 

 much lighter in colour. The fronds of the large Lami- 

 narian are frequented by lacuna vincta and its variety 

 fusca. The first is greenish or purplish horn colour, with 

 darker bands, while the variety fusca is uniformly dark 

 brown or chestnut ; the colours in both cases quite match 

 the Laminarian upon which they are found. Another 

 species of the same genus, Lacuna neritoidea, Mr. Fuller 

 has observed spawning on bladder-weed, and its yellowish 

 tinge accords well with its surroundings. Margarita 

 helicini I have found in numbers on the large Laminarian, 

 and on seaweed at low-water mark, and its colour is de- 

 cidedly protective ; while other species of Margarita, 

 dredged in deep water on shelly ground, are whitish, 

 pearly, or red. 



The protective colouring of certain species is well seen 

 upon stones dredged in deep water, the various mollusks 

 adhering to them closely resembling the calcareous algse 

 and the stones themselves. 



Species similar to sand beaches are of various sand- 

 coloured shades, as for example Machara, Mactra, Coch- 

 todesma, Cyprina, the little Solenomya, and Solen. On 

 muddy ground we notice certain Tellinas and other species 

 with white shells. It has been supposed that those species 

 hidden from the light were generally white, and this would 

 seem to be the case when we recall Mya, certain species 

 of Teredo, Tellina, PJiolas, and other species. Yet we do 

 have cases where the shell is oftentimes conspicuously 

 banded or marked. It might appear that in those species 

 living buried in the mud or sand, the shell was pro- 

 tected by a very thin epidermal layer, and that this 

 layer was eroded, thus exposing the white shell ; there 

 are certain species, however, living buried in the mud 

 or sand, which have an epidermal coat, very thick, and 

 dark brown or black : such examples are seen in So- 

 lenoniya borealis and Glycyineris siliqua. 



It has been noticed that the same species occupying 

 difterent stations are differently coloured. Dr. A. A. Gould 

 noticed this in regard to Astarte castaiiea ; those thrown 

 up from deeper water are darker coloured than those found 

 in quiet sandy places. In his " Report on the Invertebrate 

 Animals of Massachusetts," first edition, p. 78, speaking of 

 the shells found in the sandy harbour of Provincetown, he 

 says : " The colour of all the shells in that harbour is 

 remarkably light." 



A very evident case of protective colouring is seen in 

 the three species of Crcpidula found on our coast. Cre- 

 pidulafornicata is drab, variously rayed and mottled with 

 brown, and it lives attached to stones near the roots of 

 the large Laminarian, or upon stones clothed with algas of 

 similar colours, or attached to the large Mytilus. Crc- 

 pidula convexa, a much smaller species, lives on the 

 roots of seaweed. Prof. Perkins records its occurrence 

 on the black shell of Ilyanassa obsoleta. This Crcpidula 

 has a very dark brown shell, according well with the dark 

 colour of its various places of lodgment. Crcpidula plana 



