66 



THE YOUNG NATURALIST. 



Leach was so far independent of his foreign predecessors as to 

 arrange, as his friend M'Leay tells us, Pselaphida next Staphylinida, 

 which is in direct antagonism to tarsal affinities. 



But this Wm. M'Leay, another Scotchman, invites our more par- 

 ticular attention. In a paper read before the Linnean Society, Feb. 

 ist, 1825. M'Leay demonstrates the fallacy and artificiality of the 

 French tarsal system of classification. This is a most interesting 

 departure and discovers M'Leay in the light of a true naturalist. In 

 his own book, " Horas Entomologiae," which was published in 1819, 

 he not only attacks this system but elaborates another on an entirely 

 new basis, rejecting the tarsal divisions, as he explains, not only 

 because they were arbitrary, but because they were founded on mis- 

 taken data. M'Leay, in the spirit of a true modern philosopher, has 

 resourse to embryology to discover a true natural order. He takes 

 the larvae, a stage no one before had ever thought of investigating, 

 and according to those embryonic characteristics therein displayed, 

 forms his groups ; and to fit in with a larger theory, in which he 

 associated all nature, and to which we must refer again, he formed in 

 this way five divisions of the order. These were as follows : — 



1. Chilopodiform, that is such beetles whose larvae are carnivorous 



hexapods, in which are included Adephaga, Palpicornia, Brache- 

 lytra, and part of Clavicornia. 



2. Chilognathiform, or beetles with herbivorous hexapodal larvae, 



including Lamellicornia, a part of Clavicornia. 



3. Anopleuriform, whose larvae are herbivorous hexapodal, and an- 



tenniferous, which includes what other systematists call Eupoda. 



4. Thysanuriform, similaar to preceding, but with anal appendages 



to larvae, which the Anopleuriform are without, principally 

 Heteromera. 



5. Vermiform, whose larvae are worm-like, and destitute of legs or 



antennae, among these are Rhynocophora, Longicornia, and part of 



Heteromera and Malacoderma. 

 Now it is evident that the lines of cleavage indicated by such a 

 classification as this traverse the group on quite another plane than 

 that afforded by mature differentiation ; read in the light of recent 

 science it might suggest more natural affinities, but at least it dis- 

 covers in M'Leay a singular insight into the importance of embryo- 

 logy in tracing development. 



Of a similar import is this naturalist's theory of circular groups, he 

 saw how impossible it was to arrange the natural order in linear 

 series, How, for example, if the Geodephaga show a transition to 



