386 Scientific Intelligence — Zoology. 



species and the generic type, to which we are obliged to refer them, 

 are always in relation with the homogeneousness, or the reverse, of 

 the places which these animals inhabit. The more natural a genus 

 is, the more restricted will be found to be the portion of the globe 

 to which it is confined, and in it the circumstances of the soil, humi- 

 dity, and temperature, will be found identical ; the less natural a 

 genus is, the more extensively will it be found distributed over differ- 

 ent parts of the globe, under the influence of different circumstances. 



Species are found to stand in the same relation to the places 

 which they inhabit, as genera, tribes, and families. Certain species 

 are spread over a wide extent of country, and others inhabit only 

 certain very limited localities ; those which are distributed over a 

 great extent present individual varieties without number, while no 

 varieties appear among those which live in the same places. 



This leads us to the consideration of a question which has already 

 been often treated of, but has never yet been sufficiently investi- 

 gated ; we refer to the influence which climate exercises on forms 

 and colours. This influence is particularly manifest among insects 

 and the arachnides. It is very true that a multitude of small species 

 are spread from the equator to the poles, without presenting any 

 thing remarkable at these two extremes ; but it is demonstrated, at 

 the same time, that species of large size, or of singular forms, or bril- 

 liant colours, always require the conditions of high temperature and 

 much humidity. In proportion as these conditions are diminished, 

 the species become smaller and less deeply coloured. In Africa, 

 where the soil is generally dry and arid, and the heat considerable, 

 we find fewer species of large size than in inter-tropical America, or 

 in the East Indies, and the greater proportion are black, or of not 

 very bright colours.' In cold countries the large species disappear ; 

 scarcely any of brilliant colours are found ; the species of an intense 

 black also cease to be met with, till at last we find none but of a 

 shining black, greyish or brownish. 



M. Milne Edwards has observed that the species of Crustacea were 

 much more numerous towards the equator than in northern regions, 

 but that the individuals considered collectively were not less nume- 

 rous in northern regions. The same thing certainly does not take 

 place with insects and arachnides ; the species, it is true, are gene- 

 rally much more multiplied towards the equator than towards the 

 poles ; but nothing indicates that the species of the north are more 

 numerous in individuals than those of the tropics ; we are assured, 

 indeed, that the contrary is the case. — From Comptes Rendus, 

 vol. xii. page 1216. 



