74 



THE BRITISH NATURALIST. 



[April 



washed in fresh water, the shells, etc., will fall to the bottom, and this 

 sediment can be dried, separated, and thinly sprinkled on a black tray 

 for examination. Species sure to occur are the red bivalve Lasa^a, the 

 flat minute brown Skenea, just like a minute Planorbis, and the fry of 

 many species which become familiar by degrees. — B. Tomlin, 

 Llandaff. (To be continued). 



Notes on Varieties. — Recently I have looked through quite a 

 large number of volumes of Natural History Journals, looking up stray 

 facts for future reference. Among other things I find several papers 

 and notes bearing on the above subject. First, an article, written in 

 1885 by Mr. T. D. A. Cockerell, from which I extract the following : 

 " Varieties are often local, abundant at one place, and not to be seen 

 in the surrounding country ; and, strangely enough, this localness 

 seems also to a certain extent peculiar to what are generally called 

 mere monstrosities. I mean the sinistral, scalariform, and decollated 

 forms. Miss Hele, in "Science Gossip," records the occurrence of 

 three sinistral Helix aspersa, and two H . hortensis, all in the same lane, 

 and I cannot think that this was purely accidental ; there must have 

 been some reason for these shells becoming reversed, and what that 

 reason may be, 1 cannot imagine. On Chislehurst common I took a 

 specimen of the monst. scalariforme of LiviiKsa stagnalis, having the 

 whorls almost disunited, and the suture between the fourth and body 

 whorls forming an acute angle. This specimen was found in a very 

 small pond, where tlie typical form of L. stagnalis does not occur, but 

 the pond is crowded with a variety which is smaller than the type, 

 and has a deeper suture. In the same pond ray brother took another 

 scalariform L. stagnalis, and he also found a third specimen in a pond 

 not far off." This seems to strengthen the conclusion to which my 

 own observations and experiments have conducted me, that varieties, 

 as a rule, breed true, and the same may be said, to a less extent, of 

 monstrosities, they are, at least, apt to recur. As bearing on this 

 point I relate the following circumstances : — Several years ago I was 

 acquainted with a female cat which had a supplementary toe on each 

 fore-paw ; although there was, to the best of my belief, no other cat 

 in the neighbourhood having a similar peculiarity, all the kittens of 

 this cat, and I remember three litters, had more than the ordinary 

 number of toes. The supplementary digits usually occurred on the 

 fore-paws, but in one instance three had this peculiarity, and in 

 another all four. It is reasonable to suppose that by selective 

 breeding a race of such cats might have been produced. With the 

 recollection of these facts before me I see no difficulty in accounting 

 for a number of reversed shells of any one species being found in a 

 locality. Mr. Swanton, of Ballyshannon, writes in 1889, relating the 

 finding of about two dozen reversed examples of H. nemovalis annually 



