PROTECTIVE DEVICES OF THE GENUS HIPPOLYTe! 103 



haunting tufts of weeds of every hue. In the Zostera meadows it is 

 also abundant. No special preference is shown for any particular 

 colour or species of weed, and it is essentially "cosmopolitan." On the 

 other hand, H. fascigcra is seldom found in any number except among 

 tufts of coarse Corallina, with which it agrees absolutely in colour, and 

 where it is often extremely abundant. 



Thus we see that the species possessing the greater colour adapta- 

 bility (H. varians) is much the more numerous, and the more extended 

 in its range ; we may safely infer that the two latter characteristics are 

 the direct outcome of the former. H. fascigcra, being less "plastic" in 

 colouring, is on the contrary restricted in habitat to those weeds to 

 which its colour has become perfectly approximated. 



We may note further that the weeds affected by the smooth-skinned 

 H. varians, in the great majority of cases, are smooth in surface and 

 not over-grown with foreign matter. 



In marked contrast, the body of H. fascigera is ornamented with 

 tufts of brush-like hairs, especially upon the sides of the carapace, even 

 invading the surface of the eye- stalks; now if we examine a spray of 

 the coarse Corallina where this species makes its home, we will find 

 the stems covered with a multitude of abodes of tiny "messmates" — 

 porcelain-like coils of the little tube-worm Spirorbis, dull looking 

 cylinders tenanted by that lovely minature Sabellid, Othonia gracilis, and 

 crusting colonies of Bryozoa protruding ever and anon circlets of hair- 

 like tentacles — that impart, when their owners put forth their feathery 

 crowns, a minutely tufted appearance to the joints of the stem. Hence 

 when the hairy H. fascigera is at rest on such a weed the mimetic 

 adaptation is greatly accentuated. The smooth H. varians in a similar 

 environment is much more easily detected. 



As there is no doubt in my mind that the plumose hairs on H. 

 fascigera are directly useful as aids in protective resemblance to en- 

 vironment, I believe, as a consequence, that we require no longer to 

 accord to these hairs any special sensory function. Some authorities 

 have considered the hairs of this species to be auditory, and while 

 they presumably must possess a certain amount of tactile appreciation, 

 their direct utility is, I feel assured, as conducing largely to the 

 protective resemblance of the prawn to the appearance of its normal 

 habitat. 



In a future number I hope to recur to this subject and to give further 

 details regarding the habits of these interesting Crustaceans. 



