THE DISTRIBUTION OF VARIANTS IN NATURE 101 



reversal of frequency, e.g. yellow ooooo is very numerous at 

 the Viennese locus, very rare in the Bohemian, 12345 1S 

 numerous at ' Berlin-Buch,' very rare at Ratzeburg. 



(6) (a) In populations intensively studied over a limited area 

 (up to 15 X 15 miles) there is an initial tendency for adjacent 

 colonies to be alike, but 



(b) the converse is not true. 



(7) 3 (above) suggests that colonies once they have diverged 

 might give rise to races. 



(8) The extent to which boundaries are broken down (e.g. 

 by specimens being carried about by birds, wind, etc.) is 

 unknown. 



(9) It is indeed a little surprising how much community 

 there is over wide areas, and this suggests that homogeneous 

 races and colonies differing significantly in several characters 

 are not likely to be very often produced in such populations. 



2. Polymorphism throughout the range of the species. 



(a) Slugs. — The variation of the commoner European slugs 

 is not completely known ; but it has been recorded in 

 sufficient detail to enable us to state that in polymorphic 

 species such as Limax maximus and Arion ater some of the colour 

 varieties are widely spread over the range and certainly occur 

 together very frequently. 



(b) Spiders. — Bristowe (1931) has described the colour- 

 variation of the spider Theridion ovatum, on which there are 

 three types of abdomen-colour, viz. : white, striped and red. 

 Details are given of the various proportions of these characters 

 in different parts of England. 



(c) Fishes. — Norman (1931, p. 220) states that the fish 

 Epinephelus striatus has eight colour-phases, none of which can 

 be called more normal than any other. Some of the forms are 

 strikingly different. 



(d) Beetles. — Hauser (1921) has described the extraordinary 

 variation in the Asiatic beetles of the genera Damaster and 

 Coptolabrus (Carabidae). In most of the species-groups, the 

 characters which elsewhere define species and races are 

 variable. Thus in one local race of a species — e.g. in the 

 coelestis group — very plump, moderately short-legged and 

 very long, long-legged forms are found ; the elytra may be 

 parallel-sided with strongly marked shoulders, or elliptical 



