BRITISH STALK-EYED CRUSTACEA. 173 
Species recognised, described and recorded. This I may have 
no right to do, but, considering the paucity of the specimens (in 
some cases only one) from which species have been evolved, and 
considering also the remarkable effects, on variation of colour, size, 
markings, and even shape, produced by locality, climate, geological 
and zoological influences, even amongst larger and more defined 
forms than these, I am inclined to recognise the full claim of 
such important and powerful causes in producing varieties. I 
hope, on the conclusion of these chapters, to say a few words 
on such varieties among the stalk-eyed Crustacea, in which I 
shall refer to some of these points. Of course, with regard to 
the genus Crangon, I have, as already stated, very few species, 
or even specimens of the rarer ones, but from all records this 
seems to be a somewhat general feature. Most of my other 
genera are represented by large series of each species, and in 
one case where three species of one genus are described by 
early authors from the British seas, I have so many intermediate 
varieties that it is really hard to say where one species leaves 
off and the next commences. 
I find the proper method to adopt in regard to a critical or 
obscure species is to procure (when possible) specimens of various 
ages, and therefore moultings, and sizes; some changes do most 
certainly take place during moultings, even after the animal has 
reached the final stage of its existence. 
With but one or two exceptions, the several species of the above 
genus are described as being very much smaller than the common 
Shrimp, and I have myself noticed that not only does the common 
Shrimp vary considerably in different localities, but that it is 
among the immature specimens that this is most noticeable. 
Alpheus ruber. 
This beautiful and exceedingly rare Crustacean has lately 
been discovered at its proper home in one of the Channel Islands 
by an indefatigable naturalist, Mr. J. Sinel, of Jersey, from whom 
I have received two of the finest specimens ever seen as regards 
colour, condition, and size. I am also indebted to Mr. Sinel 
for some valuable notes on its power of producing sound, as well 
as on its habits so far as he has been able to observe them. 
In describing this species as Alpheus ruber, I may be con- 
sidered in error by those who have examined specimens of this 
