CLASSIFICATION OF COLEOPTERA. 215 



the Phytoi^baga, and the Rhynchophora have six. The number 

 varies in the other large groups, being usually four in the lower 

 forms, such as the Malacoderms, and six in the higher and more 

 specialized forms. So that, notwithstanding Wheeler's view 

 that six was the primitive number of the nephridial vessels not 

 only in Coleoptera but in all insects, it would seem that in the 

 Coleoptera, at least, the tetranephric condition is more primitive 

 than the hexanephric. Brauer believed that the primitive insect 

 had only two pairs of nephridial ducts. Wheeler has brought 

 forward many facts in support of his own view, but there are 

 others which tell against it, and, on the whole, I think it is 

 safe to conclude that the tetranephric Coleoptera are generally 

 more primitive than those in which the hexanephric condition 

 prevails. 



The Nervous Si/steiii. — As a result of the researches of 

 Blanchard, Brandt, and other anatomists, the condition of the 

 nervous system in many families of beetles is now fairly well 

 known. The differences found in it relate mainly to the greater 

 or less concentration of the ganglia in the ventral chain. It 

 may be assumed as true that the greater the concentration of 

 the ganglionic chain, the higher is the stage of development 

 proceeding along the same line. This consideration has greatly 

 influenced Gauglbauer in his arrangement of the family series, 

 and of the different families in each series. The Rhynchophora 

 show throughout a relatively very high concentration of the 

 ganglionic chain ; the Anthribidae, which he considers to be the 

 lowest and least differentiated of the families, being inferior to 

 none of the others in this respect. The Scolytid?e, in which the 

 concentration is greatest, he places chiefly for that reason at the 

 end of the series. The Rhynchophora he considers to be of 

 later origin than the Phytophaga, and doubtless derived from 

 them, probably through the Bruchidfe, in which already there 

 was shown a rather strongly concentrated nervous system. 



The high degree of concentration of the nerve ganglia met 

 with in all the Lamellicornia, except the Lucanida;, seems to 

 have been one of the chief factors in determining him to place 

 the Lamellicornia as the highest and last group of all. 



But the concentration of the ganglia of the ventral chain 

 seems to be correlated with a general shortening of the body, 

 especially of the hind body ; so that it probably does, as Kolbe 

 maintains, follow, merely as a consequence, the concentration 

 of the body by a fusion of its segments and parts with one 

 another. 



External Morphologij. — The characters so far considered are, 

 with the exception of the wing-venation, somewhat outside the 

 field of the ordinary systematist. But the characters with which 

 he has mostly to deal— those derived from a study of the external 

 form and structure of the body and its appendages — are scarcely 



