CH. XIX] TO ANIMALS 203 



In the Beetles the curve shows clearly in all groups counted. 

 For example, the Tenebrionidae (Gebien, Col. Cat. 15, 22, 28, 37, 

 1910-11) show 489/1, 154/2, 103/3, 73/4, 40/5, 48/6, 32/7, 32/8, 

 24/9, 10/10, and so on; the same kind of figures are shown by the 

 Coccinellidae (Gemminger and Harold, Col. Cat. 1876), and the 

 Chrysomelidae {lb. 1876), as well as other smaller groups that 

 were counted. Unfortunately, I counted the Coccinellidae and 

 Chrysomelidae from an old catalogue, and the new catalogue is 

 not yet sufficiently complete to enable a comparison to be insti- 

 tuted. The result of comparing floras of different dates and by 

 different types of systematists, however, leads one to suppose 

 that the result Avould be very similar. 



Not only does the curve shoAV in general lists of the animals of 

 the world, like these, but also, just as in the case of plants, it 

 can be seen in local faunas. Thus taking Barrett's British Lepi- 

 doptera (London, 1905), one finds that the genera whose names 

 begin with A, B, C or D show 62/1 (62 of one species in Britain), 

 28/2, 13/3, 4/5, and so on; those with E, G, H or L show 54/1, 

 18/2, 14/3, 10/5, and so on; those with M, N, O or P 63/1, 15/2, 

 9/3, 8/5, and so on; and those with R to Z 36/1, 7/2, 6/3, 4/5, 

 and so on. The total shows 215/1, 68/2, 42/3, 26/5, and so on. 



The British Echinoderms (Bell, 1892) show 39/1, 16/2, 5/3, 

 and so on. Even so small a group as the British Spiders does its 

 little best to follow the curve. It is clear that the rule holds as 

 well for animals as for plants, as Avill be seen by examining 

 the fig. on p. 237, Avhere the curves for animals and for plants, 

 for local floras and for local faunas, etc., are mixed up together. 

 The same rules have evidently guided the evolution and the 

 geographical distribution of both groups, and the extraordinary 

 parallelism of the curves goes to show that both evolution and 

 geographical distribution were largely guided by factors that 

 acted in a mechanical Avay. The very interesting suggestion has 

 been made that the parallelism may be due to the fact that 

 animals are (in the long run) a function of plants. But it does 

 not seem to me that this is quite sufficient to explain, for instance, 

 the fact that the Ichneumons show^ a curve parallel to the others. 



