344 



SCIENCE-GOSSIP. 



solubilities, that the ed colouring was not organic 

 in character ( 10 ). 



I should like here to mention Mr. Horsley's note 

 in Science-Gossip (p. 254). His paper in the 

 Malacologist for last July (vol. vi., August, 1S97, 

 p. 21) was published after the present communi- 

 cation had been written ; but I must apologise 

 for the oversight which prevented me noticing 

 his interesting suggestion in its proper place, as 

 I had fully intended to do. I cannot think that 

 his explanation is satisfactory. In the first place 

 I observe the same predilection for hedge-banks 

 in Tachea in all kinds of soils, and on all kinds 

 of roads. I have especially in mind a lane 

 which is seldom less grassy than an averagely 

 bare meadow, but on the banks of which Tachea 

 abounds. The banks with which I am chiefly 

 acquainted are on the side of roads which have a 

 surface composed of hard bluish basalt from the 

 Clee Hills. I cannot obtain any information a' 

 this moment as to its chemical composition, but 

 judging from other similar rocks, its percentage of 

 lime is not in all probability high. 



Another objection seems to me to lie in the fact 

 that it is not known — that is, to the best of my belief 

 ■ — that ordinary inorganic calcium salts are of direct 

 use to snails in making their shells. It would seem 

 much more probable that they obtain it through 

 the intermediary of plants, which often contain a 

 considerable amount, and where it probably exists 

 as an integral part of the proteid molecule ( n ). The 

 amount of calcium in a plant, it is true, varies to a 

 certain extent with the amount of lime in the soil. 

 The objection to this view, and it is, I think, a 

 very serious one, is that a snail would often 

 have to consume a prodigious amount of plant to 

 get the necessary calcium. The amount it con- 

 sumes seems to be very large, and it may be large 

 enough ( 12 ). Finally, I can call to mind several fields 

 with which I am very familiar which have 

 been on occasions treated somewhat freely with 

 lime stuffs, but the grassy hedge-banks remain as 

 snailless as before. The matter seems to me to be 

 one of vegetation : we find Tachea abundantly in 

 places where the plants are varied, and in a sense 

 rough and coarse, and often rather sparse, e.g., 

 on many roadside hedge-banks, on sand-hills, in 

 disused overgrown quarries, on railway banks; but 

 we do not find them in any quantity in grassy 

 meadows, nor on hedge-banks which are thoroughly 

 grassy, nor often on such hedge-banks even where 



( 10 ) Though rather foreign to the subject, Mr. Nance's 

 main analysis of a white shell may be thought worth publish- 

 ing : — Water, 1-34 ; Organic matter 4*00 ; CaC0 3 , 93'ot ; A1 S 3 , 

 I '58 = 99'93- The analysis was made some twelve months 

 after cleaning out the shells. 



{ n )Cf., e.g., E. A. Schafer, "Text-Book of Physiology," i. 

 (1898). p. 886. 



( u ) Exact data are difficult to get, but it would appear that 

 about two kilos, of ordinary average grasses would supply the 

 lime for a large Tachea nemoralis. 



C 3 ) As has already been pointed out by C. E. Wright, 

 Science-Gossip, N.S. iv. p. 336 (1898). 



they abut on the highway. Tachea seems to revel 

 in variety in more than one way, and to be very 

 precocious as well. There also seems to be more 

 humus in such places ; though, seeing that Tachea 

 is mostly absent from the places where humus 

 chiefly abounds, this cannot go for much. 



It seems to me that Mr. John T. Carrington's 

 suggestion in the same place is hardly in accordance 

 with observation ( 13 ). Thrushes and blackbirds do 

 not seem to shun the roadsides much, as, indeed, 

 is testified by the frequency of their nesting in these 

 public places ; and they will come to get food into 

 the very near proximity of man and his works. 



While on this subject, I may mention that I often 

 think I can detect a very marked predilection in 

 Cryptomphalus aspersus, and, to a less degree, in 

 Fruticicola rufescens for the neighbourhood of human 

 dwellings or buildings. I do not know whether 

 this is in accordance with the observations of 

 others. It may be only that Cryptomphalus aspersus 

 are so very easy to see when they are in the 

 situation to which one always turns to find them — 

 at the bottom of an old well. But it seems to me 

 that there is more in it than that. 



This article must conclude for the time being 



my series on the coloration and variation of our 



land and fluviatile mollusca. I hope, however, to 



return to the subject in these pages at a future date. 



The Grange, Hereford ; April, 1898. 



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