Manganese in Land and Fresh Water Mollusca. 15 



localities. Nitidus and lucida are the lowest, while excavatus 

 showed 127 parts from Carnarvon and as much as 185 (1*85 per 

 cent.) from Cheshire. Bidiminus montanus and obscurus both 

 give very high figures, while Claiisilia laminata and Succinea 

 have a moderate amount, and Cyclostoma only a little. Among 

 the slugs, Testacella has least, ater, hortensis, sowerbyi and 

 agrestis a fair quantity, maximus a large amount, while 

 ciner eoniger , arborum and subfuscits give very high figures. The 

 last three species are, however, represented from a single 

 locality only, and the figures are therefore unreliable. For 

 this reason it is not possible at present to draw any distinction 

 between the Arionidae and the Limacidae. Vitrina has only 

 a little, something about 2. 



(b) Among the water snails, Ancylus fluviatilis gives far the 

 highest amount (21), and Bithinia and Physa hypnorum very 

 little. Planorbis and Limncea all show a moderate quantity, 

 PI. cornens the most, with a large difference for the two localities 

 -examined. The general position for the water snails is that 

 they have more than the Helicidae and less than the Zonitidas. 



(c) The bivalves fall into two very distinct groups — (1) those 

 with much (Anodonta, Unio) and (2) those with little or none 

 (Sphceriiim and Pisidinm). A. cygnea, for example, may have 

 1 per cent, and Sph. corneum may give a negative reaction with 

 as much as o-8 gramme, i.e. something less than 6 per million. 



I have made only a few casual observations on the dis- 

 tribution of manganese within the body. 1 If the carcase is 

 roughly divided into (a) the head, neck, foot, with the lower 

 part of the genitalia ; (c) the apical part, consisting of liver, 

 intestine and hermaphrodite gland and (b) the rest, we find most 

 in the liver and least in the head. Thus, in a series of stagnalis : 



Parts Manganese per 10,000. 

 (a) heads. (6) middles, (c) tails, whole. 



Shells 18 mm. long ..faint trace ( < o-6) 9 16 8 

 30 . . trace ( < 0-3) 7 13 6 



40 . . trace ( < 0-3) 6197 



The liquid obtained by gently crushing others of the same 

 lot yielded none, which suggests that there is no manganese 

 in the blood. The same preponderance in the liver was found 

 in nemoralis (3-1 against 1-8 for the whole body), cantiana 

 (3-0, i-i and 3-4, 07), aspersa (3-1, 0-9 and i-8, 07), pomatia 

 (4-5, 2-5), helvetica (63, 49), lucida (13, 7), lapicida (22, 12), but 

 not in Arion ater, where the distribution was pretty uniform 

 all through the bodies of two specimens, nor in Limax maximus, 

 one of which (v. fasciata) gave a uniform distribution, while 



1 In mussels, Bradley (loc. cit.) found it in all organs, but mostly in 

 the liver and mantle. 



1917 Jan. 1. 



