HARDWICKE'S SCIENCE-GOSSIP. 



179 



usually, as far as my experience goes, below the 

 periphery. ) 



There is a pond at Bromley where Z. peregra 

 occurs. The specimens are very variable in shape, 

 and are covered with some kind of growth which 

 makes them appear almost black outside, and greyish 

 within. They are infested with a parasite, which my 

 brother tells me is a very beautiful microscopical 

 object, but I have not yet examined any microscopi- 

 cally myself. Some of these shells have a very 

 expanded lip, and belong to the var. labiosa, Jeff., 

 and in some cases the lip of the shell is even reflected 

 upon itself, so that the mouth presents a rounded 

 edge formed by the inner surface of the lip which by 

 the reflection becomes outermost. 



Z. auricularia. The var. acuta is recorded for 

 Kent. Specimens from Regent's Park have a rather 

 long spire and are pale in colour. 



Z. stagnalis. Var. fragilis has been taken in 

 Middlesex and Surrey. Monst. scalar if or me, Chisle- 

 hurst (S.C.C. and T.D.A.C). Monst. decollatum, 

 Barnes. 



A variety (which might conveniently be called 

 expansa)* lives in a small pond at Bromley, where the 

 type form does not occur. It has a short spire, 

 the body whorl is large and expanded, and the mouth 

 of the shell wide ; the length of the spire is about | of 

 the total length of the shell, which is somewhat less 

 than an inch and a half. The only weed I noticed in 

 the pond was Lemna minor. A specimen of Z. 

 stagnalis taken at Deal is slender in shape, light in 

 colour, and has a shallow suture. Shells from a 

 small pond on Chislehurst Common, on the contrary, 

 are dark in colour, and have a deep suture (two 

 specimens being actually scalariform, as stated above), 

 and these shells are a good deal smaller than the type 

 form ; some specimens, apparently full grown, being 

 about two-thirds of an inch in length, although others 

 are much larger. Should these be found elsewhere, 

 var. elegantula would perhaps be a suitable name for 

 them.f Another pond, also on Chislehurst Common, 

 produces quite a different variety. This form has a 

 very shallow suture, and is not unlike some varieties 

 of Z. palustris. It is never so large as the typical 

 stagnalis, the usual length being little more than an 

 inch. Why these two ponds, only a few hundred 

 yards distant from one another, should produce two 

 forms so totally distinct, I cannot imagine ; the soil 

 appears to be the same, and the only difference I can 

 detect is that the one having the first variety is in the 

 open, is very small, the Limnseaj being very crowded, 

 especially in the summer, when the pond is almost 

 dried up, and the food plants are Potamogeton and 

 Ranunculus. The second pond is partly under the 

 shade of a chestnut tree ; it is much larger and not so 



* Unless it should prove identical with the variety lacustris 

 of Moquin-Tandon, or the variety fucincns is of Paulucci, both 

 of which it resembles, in some respects at any rate. 



f Mr. Taylor, of Leeds, is of opinion that this form does not 

 differ from the var. botanica of Clessin. 



crowded, and the principal food-plants are Anacharis 

 and Callitriche. 



From a third pond on Chislehurst Common I took 

 a specimen having whitish bands below the periphery, 

 like the Walmer Z. peregra. Specimens from Grove 

 Park have a pointed and slender spire, and the lip 

 tinged with pink. 



I will now venture to say a few words about the 

 naming of varieties. There are some who would 

 name every variation that can be defined, and others 

 go to the other extreme, and will have nothing to do 

 with varietal names. To me it seems that as every, 

 or nearly every species has one or more marked 

 variations from what is called the " type," and 

 likewise a number of less definite varieties connecting 

 one form with another, it is extremely difficult to 

 find an intermediate course between giving names, or 

 ignoring them altogether. Suppose, for instance, in 

 the present paper, I had refused to accept any 

 varietal names, but had written out a full description 

 of each variety, what a deal of space would have been 

 uselessly expended ; and the difference between the 

 space taken up by the names of described forms and 

 descriptions of undescribed ones, is well shown above. 

 "But," some reader will exclaim, "you will be 

 naming almost every shell that passes through your 

 hands, and my memory will be burdened with 

 thousands of names which are really of no impor- 

 tance ; and although a species is a tolerably fixed 

 point, varieties are infinite, and naming them can 

 only end in confusion. " These are sentiments I have 

 heard expressed. 



I would reply to this, that the varietal names are 

 principally of use to specialists, for it is manifest that 

 a general student of conchology is scarce able to 

 study all the variations of all the species ; but to one 

 studying any particular genus or species, the varietal 

 names are most useful and almost indispensable. 

 In proof of this I will ask, How many specialists 

 have been obliged to make varieties, and how many 

 have done without them ? I fancy the former are in 

 the majority. And some think that a species is a 

 fixed point. To these I would recommend the study 

 of Pisidium. Others say that varieties are of no 

 importance ; I contend that they are of the greatest 

 importance, but I cannot enter here into the reasons 

 why they are obvious enough to most people. 



As for burdening the memory, this is an 

 equally good argument against bringing forward any 

 information whatever, and against names in general. 

 Lastly, I would remind those who do not already 

 know it, that all names, generic, specific, or varietal, 

 are merely a matter of convenience, and although it is 

 open to anyone to propose names, no one is obliged 

 to accept them unless he finds it convenient to do so. 

 Some people, however, seem to think that a sort of 

 mysterious change comes over a specimen when it has 

 a name tacked on to it, and its value goes up 95 per 

 cent. I think it would not be a bad idea if at periodical 



