208 K. E. VON BAER. PHILOSOPHICAL FRAGMENTS. 



course of the urine would then seem especially to be towards 

 the left. If the principal activity of the kidneys should consist 

 in attracting venous blood, merely allowing the urine to transude, 

 they would come under the general law*. 



Enough of the demonstration that the organic current in the 

 plastic part of the Vertebrata has a direction especially towards 

 the right side, in order to show that the arrangements of the 

 molluscous type prevail in this half of the vertebrate animal. 



We have now considered the four archetypes, and it will be 

 sufficient for our purpose to remark shortly, that these arche- 

 types become modified in the subordinate forms, like the varia- 

 tions of one theme. Thus the segments of the Articulate series 

 sometimes more resemble one another, as if they were strung upon 

 a thread, sometimes they are collected round a central point. 

 In this manner variations of the archetypes are formed, which 

 may be conceived to be arranged round them, and some of which 

 are more nearly approximated to them, representing more purely 

 the character of the archetype, while others are further removed. 

 These subordinate types, combined with a determinate degree of 

 development, yield what we call the classes of animals. In these 

 it is sometimes one, sometimes another vital condition which is 

 more developed ; or more justly, the development of life in this 

 or that direction produces the variations of the archetypes, just 

 as these are themselves essentially different in the vital pheno- 

 mena which they manifest. Thus among the Vertebrata it is 

 plainly the Birds, in which the relation to the air is predominant. 

 It penetrates their whole body, and for it the anterior motor 

 organs are constructed. So with the true winged Insects among 

 the Articulata. The classes of animals again are divisible into 

 smaller variations, which we call families, in which not only the 

 archetype but the type of the class is exhibited, together with 

 peculiar modifications which constitute the character of the 

 family. Smaller modifications in this family character yield the 

 genera. And so it goes on down to the species and subspecies. 



* The preponderance of the right kidney is not universal even in the 

 Snakes. At times their length is balanced by the greater thickness of the 

 left kidney, as I observe in Vipera Berus. In Tortrix Scytale, however, the 

 preponderance of the right kidney is, I find, according to Meckel and Finke, 

 evident. It is remarkable that the urinary system is the only one which is 

 aberrant in the peripheral type also. 



