GENERAL IDEAS. 587 



The physiological principles whence the natural system proceeds 

 are : 



1. That the entire organisation takes its origin from a most simple 

 beginning, whence by the development of this into several organs, it 

 elevates itself to its most perfect form. This development exhibits itself 

 partly in the internal and partly in the external organs, and almost 

 throughout presents itself in antitheses, for instance, insects with a 

 metamorphosis and insects without a metamorphosis ; the former are 

 again divided into those with a perfect and those with an imperfect 

 metamorphosis, &c. The more these antitheses are divided the more 

 do they seek to re-unite, in the first place, to preserve their original 

 unity, and in the second place to produce a new antithesis, as, for 

 instance, both groups into insects with haustellate oral organs and with 

 rnandibulate oral organs, each of which again strives to approach the 

 other. Thus lower groups with individual superior organs stand oppo- 

 site in equal value to the lower groups of the superior grades. 



2. This equivalent value produces the mutual relations of the groups, 

 which re-produces their more intimate concatenation. 



Thus we find insects with an imperfect metamorphosis possessing 

 mandibulate organs, which, from their second degree of development, 

 strive to rise above those with a perfect metamorphosis and haustellate 

 oral organs, as, for instance, the Orthoptera are placed by the majority 

 of systematists above the Diptera and Lepidoptera, which, however, is 

 inadmissible, from their imperfect metamorphosis. 



3. The external organisation can attain a higher grade, while the 

 internal remains stationary, and thus mark the prefiguration of a 

 superior group in one that is inferior. It thence happens that the natural 

 system does not ascend in a direct line from the most simple to the 

 most complex group, but sends forth on all sides lateral branches, 

 which, proceeding from a lower grade, strive to attain the highest. 



According to these principles, which we have thus made to harmonise 

 with the views of modern systematists, was the system sketched that 

 we formerly published *, and which we shall have an opportunity of 

 presenting, in the historical survey of systems. 



Upon passing from these general observations upon the nature and 

 difference of both divisions to the groups characterised in both, we 

 shall find them to consist of the following : 



* De Inscctoi-uin systcmute naturali. Hula-, 1920. Ovo. 



