l8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



related species .... bear a striking resemblance to the plants (es- 

 pecially Zostera leaves) on which they are found" (p. 78).' 



" Many Crustacea," according to Parker and Haswell, " present 

 instances of protective and aggressive characters, i. e., modifications 

 in form, colour, etc., which serve to conceal them from their enemies 

 or from their prey. Probably the most striking example is that of 

 certain crabs (Paramifhrax) which deliberately plant Sea-weeds. 

 Sponges, Alcyonarians, Zoophytes, etc., all over the carapace, and 

 are thus perfectly concealed except when in motion." ^ 



Poulton expresses the same view in the following language : " Cer- 

 tain palatable animals make use of the Special Defence and Warning 

 Colours of other forms. Thus, the common English hermit-crab, 

 Pagurus hcruhardus, commonly carries on its borrowed shell the con- 

 spicuous stinging sea-anemone Sagartia parasitica; while another 

 English species, Pagurus pridcaiixii, inhabits a shell which is invari- 

 ably clothed by the flattened Adamsia pallia fa. Two crabs {Polydectus 

 cupulifer and Melia tessellafa), from Mauritius, described by Mobius, 

 invariably held a sea-anemone in each claw. Two other groups of 

 animals, sponges and Ascidians, in addition to sea-anemones, are 

 avoided by enemies of the Crustacea, and these are also employed 

 by the latter. Thus the British hermit-crab Pagurus cuanensis is 

 found in shells which are covered with a (generally) brightly-coloured 

 sponge {Suherites domuncula). Mobius also describes a Mauritian 

 hermit-crab (Ascidiophilus caphyraefonnis) which lives in a case 

 formed by an Ascidian." ^ 



Bird enemies. — Most of the leading subdivisions of the Crustacea 

 contribute to the food of birds, apparently about in proportion to their 

 accessibility. The tabulation of numbers of species of Crustacea used 

 for comparison with those of percentages of identifications was made 

 from "A list of the Crustacea of New Jersey including the adjacent 

 region or that of the Middle Atlantic States," ' the onlv clicck list 

 available for any considerable area of our region. 



The Anostraca (fairy shrimps) are locally eaten more extensively 

 than indicated above and the fact is an illustration of the principle 



* Morteiisen, T. H., Observations on protective adaptations and habits, mainly 

 in marine animals. Vidensk. Meddel. fra Dansk. naturli. For. Kjob., 1x1. 69, 1920. 



^Zoology, vol. I, p. 601, 1910. 



' Ponlton, K. B., Essays on evolution, pp. 356-357, 1908. 



Thomas Scott records a copepod (Acidicola rosea) which lives within the 

 branchial sac of an ascidian as having been eaten by a sole Plenroncctes micro- 

 cephahis. (20th Ann. Rep. Fisliery Bd. Scotland, p. 525, (igoi) 1902.) 



* Fowler, H. W., Ann. Rep. N. J. State Mus., pp. 463-598 (1911), 1912. 



