2IO Boycott : Manganese in Land and Freshwater MoHusca. 



the lowest from a garden in Ireland (6), and from eight 

 different beech plantations in South Wiltshire (under i to 13). 

 It is suggestive also that the ten analyses of that domesticated 

 slug Limax flavus all give less than 6 except one from Cork (36) 

 which is tire only example from a wild place that I have 

 examined, and that Testacella, Agriolimax agrestis, Amalia 

 sowerbyi and A. gagaies, which arc fond of cultivation and 

 civilisation, all give low figures. Limax cinereoniger , which 

 is markedly anthropophobous, has given no result less than 14. 



If these indications of a connection between old woods and 

 abundance of manganese represent any reality, a number of 

 possible explanations suggest themselves, of which two are 

 worth mention, (a) Many places are uncultivated because 

 they are uncultivatible ; possibly an excess of manganese in 

 the soil is the cause of this, {b) Trees may collect manganese 

 from the soil, and it then accumulates in the humus — on the 

 whole I think the most likely explanation. I do iu:)t suppose 

 that there is a direct connection between any mollusc and the 

 content of any place in manganese ; the association, such as 

 it is, is indirect via the soil or vegetation. 



The most richly manganiferous place which I have met with 

 is Blackberry Castle, a mixed beech-oak-birch-sycamore 

 (originally, I expect, oak) wood on a sad, gravelly soil of 

 ' clay with flints ' overlaying the greensand four miles north- 

 west of Seaton, in Devon. The results are as follows, the 

 general average for each species being given in brackets :— 

 Limax cinereoniger 85 (46), L. tenellus 137 (87), L. arborum 

 96 (57), Hyalinia cellaria jy (21), H. helvetica 133 (24), H. 

 alliaria 145 (36), H. nitidula 199 (35), Arion ater 364 (31), 

 A. sitbfnscus 292 (58), A. hortensis 228 (29), A. circttmscriptus 

 113 (12), .4. minimus 162 (44), Pyramidula rofundata 4 (2). 

 Contrast with this Tower Hill Wood, a beech wood largely 

 and perhaps entirely a modern plantation on the chalk downs 

 two miles west of Boscombe, in south-east Wiltshire: Limax 

 maximiis 2 (13), L. arborum 2, H . cellaria 11, Arion subfuscus 2, 

 A. hortensis ^, A. circiimscriptus 5, Agriolimax agrestis 4 (9), 

 Hygromia riifescens i (0.4), Helix nemoralis 1(1), H. Jiortcnsis 

 I (i), Buliniimis obscurus 56 (61). 



The species which live in wet places by the sides of rivers, 

 etc., Agriolimax laevis, Zonitoides nitidus, Ashfordia granulata, 

 Succinea piitris and S. elegans, seem to separate themselves out 

 as a habitat, rather than a systematic, group of rather low 

 manganese content. I have already noted that Hyalinia 

 cellaria, Hy. helvetica and Hy. nitidula from such places give 

 results much below the average. 



Among the species which were not included in my previous 

 paper, Margaritana margaritifcra is of interest. Li\'ing in 

 soft-water rivers in the west and north, it falls in line with the 



