^M THE NEW EVOLUTION ^^^^ 



The discontinuity of the forms within the species 

 as they normally exist in nature is emphasized by 

 very many cases in which the forms produced are 

 extremely local, or are rare varieties, or are sporadic 

 aberrations. 



Professor William Bateson has brought together 

 some significant cases of such variations. He pointed 

 out that reversed varieties of animals are frequent. 

 They are not uncommon in man. They are especially 

 noticeable in the mollusks and the flat-fishes. Such 

 varieties are formed as optical or mirror images of 

 the body of the usual form. In both the mollusks 

 and the flat-fishes some species are normally right- 

 handed, while others are normally left-handed. But 

 reversed examples are found as individual variations. 



In the mollusks this is not confined to the gastro- 

 pods or snail-like mollusks (fig. 51, p. 97), which 

 have spiral shells, but occurs also in the slugs and in 

 the bivalved mollusks (fig. 5x, p. 97). 



Bateson noted that the fact that the reversed con- 

 dition may become a character of an established race 

 is familiar in the case of Fusus antiquus. This shell 

 is found in abundance as a fossil of the Norwich Crag. 

 The individuals in the Crag are normally left-handed, 

 though the same species at the present day is a right- 

 handed one. Of the left-handed form a colony was 

 discovered on the rocks in Vigo Bay, where the indi- 

 viduals were associated with certain other shells 

 occurring in the Norwich Crag. The same variety 

 occurs in Sicily. 



Bateson remarked that from time to time there 



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