igS JOURNAL OF CONCHOLOGY, VOL. it, NO. 7, JULY, I905. 



and (c) have dark lips. And though this does not prove that Coutagne's 

 113 black-h"pped Jif. horioisis were hybrids, it shews that the argu- 

 ment by which he seeks to prove that they are not, is invalid. 



- It is not uninteresting to compare, in the light of the suggestion 

 that all black-lipped H. hortensis are hybrids, this statement of 

 Ashford : — " The rapid fading of the peristome tint appears to be 

 peculiar to H. hortensis as distinguished from H. nemoralis. In fact 

 it is an accidental colouring in the former case, and a normal one in 

 the latter'V with a number of cases collected by Giard, and described 

 in a paper entitled "Caracteres dominants transitoires chez certains 

 hybrides."- 



Remarks on Professor Lang's Memoir. 



There are two points of view from which the phenomena of heredity 

 may be regarded, the Mendelian and the biometric ; and the manner 

 in which material is collected by one who looks at it from the one 

 point of view is not the same as that employed by one who regards it 

 from the other.^ The way in which Professor Lang's data were col- 

 lected does not admit of their description in terms of the law of 

 ancestral heredity.^ 



The results obtained with the five-banded and unhanded varieties 

 of H. hortensis afford an instance of what has been called the 

 Mendelian phenomenon ; but when Professor Lang states that they 

 constitute a " brilliant confirmation of a part of Mendel's law" he 

 makes a statement the truth of which depends entirely on our con- 

 ception of the expression "Mendel's law." If he does not mean 

 any more than that the phenomenon he is dea'ing with is the same 

 as others which are called Mendelian, I believe his conclusion is 

 justified ; but if he means that his experiments afford conclusive 

 evidence of the existence in the gonads of Helix hortensis of definite 

 unit-bearing elements representing either five-bandedness or un- 

 bandedness, I do not believe that he is justified. 



That the explanation of these phenomena is not so simple is made 

 probable by comparing the differences between the parentages in 

 matings of type 0x5, which gave both o and 5, with those which 

 produced only o. The simple Mendelian explanation which naturally 

 suggests itself, and which Lang himself suggests, is that in the first 

 case the o was DD and in the second DR. There is no a posteriori 

 evidence for this to be derived from an examination of the parentages 



1 " British Land and Freshwater Shells," by L. E. Adams, p. 72. Adams has confirmed 

 Ashford's statement. 



2 Coniptcs Rendus Soc. Biol. Stance du 2S Mars 1983, vol. 35, p. 410. 



3 See Darbishire, Manchester Memoirs, so\. 49, no. 6, p. 17, 1905. 

 t^ Karl Pearson, Biomctrika, vol. 2, p. 211. 



