DAR'RISHIRE : PROFESSOR LANG's BREEDING EXPERIMENTS. igf 



1. In certain stations, such, for example, as those studied by Miiller 



in Denmark, there exist two groups of Helices, of which we will 

 call the one H. itemonilis and the other H. hortensis, between 

 which intermediates are not found. In the former group, the 

 shell is larger, more depressed, the epidermis less shiny, the 

 lip brown or black \ in the latter, the shell is smaller, more 

 globular, more shiny, and the lip is white. 



2. In other localities, in the neighbourhood of Orsay, for example, 



these two groups of Helices live together, and still present the 

 same peculiarities and differences ; but there occur besides a 

 certain number of intermediate forms, apparently hybrids, 

 the paucity of whose numbers, no less than the complete 

 absence of intermediates in the preceding case, points to the 

 existence of a real genealogical barrier between the two groups. 



3. The differential characters which enable one to separate 



H. neinoralis and H. hortensis with certainty when they are 

 found associated in one colony are vaiiable "and subject to 

 inversion, in such a way that it is not always possible to dis- 

 tinguish with certainty from the shell alone,^ the H. neinoralis 

 from a station a, for example, from the H. hortensis of station b 

 of another locality if one has not got as points of comparison 

 the H. hortensis of station a or the neighbourhood, and the 

 H. nemoralis of station b or the neighbourhood.-^ 

 An actual case which illustrates the state of affairs on which the 

 third generalization is based is the following : — Coutagne collected 

 in one locality, on April 22, 1879, 242 H. hortensis and 26 H. nemo- 

 ralis. Of these 242 H. hortensis, 113 were of a lemon-yellow colour, 

 were unhanded, and had dark lips ; while of the H. nemoralis, nine 

 shells had five bands ; three had four bands \ seven had three bands ; 

 one had two bands ; and six had no bands. 



Coutagne's verdict on this case is : — " The H. hortensis of the 

 form melanostonia are not hybrids ; for these black-lipped individuals 



are all unhanded , whereas the H. nemoralis are banded in 



the proportion of sixty-one per cent.'' If the H. nemoralis tvere 

 parents of the rij individvals tvhich I have called H. hortensis var. 

 raelanostoma, there is every reason to believe that this character of 

 banding would appear at least in some cases in these iij individuals."'^ 

 Now, Lang has shewn that the offspring resulting from the union 

 of a five-banded H. nemoralis and an unhanded H. hortensis are : 

 {a) unhanded; ib) like H. hortensis in the form of the shell and mouth; 



1 i.e., witliout the dart. 



2 Quoted from Lang's Memoir, p. 499. 



J i.e., in the l'6 snails there were So band;; out of a total po^bible iju — _-6 X 5. 

 4 Pily italics. 



