Problems of genetics / by William Bateson.

  • Bateson, William, 1861-1926.
Date:
1913
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Problems of genetics / by William Bateson. Source: Wellcome Collection.

    150/290 (page 128)
    128 PROBLEMS OF GENETICS midata. In France generally they are distinct enough from each other, trochoides being smaller and having a characteristic keel. Cou tagne says that after having collected these species from more than a score of localities he came upon a colony of trochoides on the island of Pomègues in which the shells were relatively enormous, most of them having only a slight keel, and a few none at all. On the other hand he received a con¬ signment of pyramidata from four localities in Sicily, all small, and one of them exactly like the trochoides from Pomègues. Judging by the samples received from Sicily, trochoides is there not more variable than it is in Provence, while the Sicilian pyramidata is protean. The relations of the two species Helix nemoralis and hortensis provide an illustration of another kind of manifestation of local peculiarity. H. hortensis and nemoralis as usually met with, are two very distinct forms. H. hortensis is smaller and duller, and its peristome is white. H. nemoralis is larger and more shiny, and its peristome is brown. In several anatomical points, moreover, especially in the shape of the dart, there are great differences. For a full account of these peculiarities of the two forms and a discussion of their inter-relations the reader is re¬ ferred to the elaborate work of A. Lang^^ who has studied them extensively and has also succeeded in experimentally raising hybrids between them. These hybrids were in a slight degree fertile with both the parent species, but up to the time of pub¬ lication no young had been reared from hybrids inter se. Coutagne describes the result of collections made in 62 French localities. Some had exclusively hortensis, some ex¬ clusively nemoralis, and in some the two were found in associ¬ ation. He gives details of five of these collections from which I take the following summary of the more essential facts, omitting much that is almost equally significant. Locality A, near Honfleur. Both forms present, each sharply and normally distinguished, without any intermediates. They A. Lang, Die Bastarde von H. hortensis Midler H. nemoralis L. Jena, G. Fischer, 1908; with a fine coloured plate showing the varieties of the species and their hybrids.