I894-] 



THE BRITISH NATURALIST. 



121 



species corydon, but has taken on to a great extent the colouration of L. adonis. It 

 was captured in cop with a female L. adonis, at a time when L. adonis was very 

 abundant, and some weeks before L. corydon occurred (vide Ent. Record, iv., p. 230). 

 The question having been raised by the President as to the number of meetings of 

 the Society which it was desirable to hold during the year, and the most convenient 

 dates for such meetings, a long discussion on the subject ensued, in which Mr. Water- 

 house, Mr. Salvin, the Hon. Walter Rothschild, the Rev. T. Wood, Mr. S. Stevens, 

 the Rev. J. S. St. John, and others took part. — H. Goss, Hon. Secretary. 



MANCHESTER CONCHOLOGICAL SOCIETY. 



ALBINISM IN MOLLUSCA : FINDS IN THE MARPLE CANAL. 



At the last monthly meeting of the Manchester Conchological Society, held at Owens 

 College, Mr. Thomas Rogers in the chair, Mr. K. Hurlstone Jones read an interesting 

 paper upon Albinism in Mollusca, and the Tendency to the Phenomenon in 1893. He 

 said albinism may be briefly stated to be lack of colour, and is really an abnormality. 

 The eye of an albino is proverbially pink, due to the blood vessels being plainly visible 

 through the transparent iris. Were any pigment present such vessels would be obscured 

 by it, and the eye would appear white. It is true that there are albino species — instance 

 the white rat, mouse, ferret, and rabbit — but these are merely artificial propagations of 

 abnormality by man. There are also many white animals, such as the polar bear, and 

 numerous birds, but these are not albinos. The polar bear has brown eyes, black claws, 

 and the mucous membrane lining the lips is of a similar colour. Some animals are white 

 at one season of the year and brown at another, as the Ptarmigan and Alpine hare, but 

 are not true albinos. Many species of mollusca occasionally produce a white or trans- 

 parent white shell, which conchologists recognize as an albino ; but a mollusc bearing such 

 a shell presents a paradox, for, whilst the shell may be perfectly colourless, the animal 

 is always more or less pigmented, in fact, the albino mollusc is in precisely the same 

 position as the polar bear, and practically, what is usually considered an albino mollusc 

 is not an albino at all. There are also shells which are partly albino and partly typical in 

 colour. Planorbis cornens, taken from a pond at Birch, were partly white and partly 

 brown, as if the collar had been unable at some parts to produce the colouring material 

 through some constitutional deficiency in such parts. Similar cases occur among 

 terrestrial mollusca, and it is more likely that these changes are due to some constitutional 

 change in the animals themselves, than to some loss in food material as has been 

 suggested ; for if the latter were the case we should expect to find a colony of the animal 

 presenting the above remarkable features. Food does, however, have considerable 

 influence on colouration, as has been experimentally proved by transporting an animal 

 from its native habitat, and feeding it upon something different to what it would procure 

 in a state of nature. Brown Helix nemoralis fed upon cabbage leaves completed the shell 

 of a yellow colour. Obviously something was wanting in the food, for this peculiarity 

 was not confined to one or two individuals, but was common to the whole brood. It may 

 be urged that a similar explanation will suffice for those specimens which have been 

 captured at large presenting the same features, but this can hardly be, for the animals do 

 not wander far except to search for food. White shells are taken either singly or in large 

 colonies. At Birch there is a pond in which the white variety of Planorbis corneus occurs 

 in such quantity that last year the number was greater than the type, being as much as 

 seventy-three per cent, of the total, and a similar tendency to form colonies has been 

 remarked amongst land shells. Probably these colonies have come into existence by the 

 accidental production of several albinos, which have chanced to interbreed, and so 

 propagated the variety. He described the structure and colouration of the shell in 

 molluscs at length, and exhititcd a large number of albino specimens taken by himself 



