Scudder.] 386 [January 22, 



stance in Europe — must undoubtedly be considered an emigrant from 

 the same warm regions; the members of tlie genus Gryllota/pa, on the 

 contrary, are found throughout the whole world, not excluding Central 

 and South America. 



Comparing these two genera with their nearest allies, Tridactylus, 

 C'l/lindrodes, etc., we find great and striking differences — dilFerences 

 which are exti-aordinary compared Avith those which divide Scapteris- 

 cus and Grijllotalpa ; the comparatively simple fore tibia, and the 

 abnormal appendages which supplant the hind tarsi in Tridactylus — 

 the abbreviated legs fitting into cavities in the body, and the absence 

 of articulated appendages at the extremity of the abdomen in Cylin- 

 drodes — these characteristics are far more important than the sexual 

 sculpture of the abdomen, the ultimate neuration of the tegmina, the 

 length of the legs, the contour of the trochanters, or the digitation of 

 the tibiaj, which separate Scapterkcus and Gryllo!alpa. 



The facts cited above present two features which bear upon the 

 question of the origin of species. 



First: these little mole crickets, so unique in their structure as to 

 be widely separated from their nearest allies, are spread uniformly 

 over the whole surface of the globe ; but few species occur in any one 

 place, and at least one is found in every temperate or hot region. 



Now, if species originate or change from physical causes, or by 

 "Natural Selection," Avhy is it that under every physical condition 

 and surrounded by every variety of antagonism possible in their 

 habitat, this same unitpie structural form has sjirung up all over the 

 globe ? 



A"-ain, how can such theories account for another feature — com- 

 mon, indeed, to all natural groups — that it is not one striking 

 characteristic Avhich separates Scapteriscus and Gryllolalpa., and 

 which "Natural Selection" might have seized upon, with reference to 

 some special benefit, but a combination of features which have no 

 apparent dependence upon each other, correlated, but not necessarily 

 connected V Why should "Natural Selection," altering for its own 

 purpose the palm of the four-fitigered mole cricket int(j that of the 

 two-fingered species in South America; or, developing in South 

 America, from some previous synthetic form of mole cricket, both the 

 present foui'-fingered and two-fingered species, and in other parts of 

 the world the four-fingered species only — destroying at the same time 

 the primaeval form all over the surface of the globe — at the same 

 time, place rows of hairs on the hinder part of the abdomen of the 

 tetradactylate group, and none on that of the didactylateV or make 

 the veins of the tegmina of the $ of one group distant and in-egular, 

 and those of the other straight and approximate V Why furnish the 

 eighth abdominal segment of the <J of one with a projecting tooth, 



