K. E. VON BAER. PHILOSOPHICAL FRAGMENTS. 



I. The Relations of Affinity among the Lower Forms of Animals. 



[From the Beltrdge zur Kenntmsa tier niedern Thiere, von K. E. VON BAER, 

 Nova Acta Physico-Medica, 1826, t. xiii.] 



From the time when the author of these essays first began to 

 occupy himself seriously with the study of the animal world, he 

 thought he could observe that the ordinary conception of the 

 mutual relations of animal forms was not true to nature, and 

 peculiar views concerning the so-called affinities of animals arose 

 in his mind. So far back as the year 1819, he began to print 

 these views, but ceased his attempt when he had reached the 

 fourth sheet, partly because the development of these principles 

 led him further than he had expected, partly because he desired to 

 make further personal investigations. Since that period, how- 

 ever, his conception of the mutual relations of animal forms, 

 remaining fundamentally unchanged, has more and more per- 

 fected itself. This is not the place, nor is there sufficient room 

 here to demonstrate it completely, for the proving of the prin- 

 ciple appears to him to be at present the chief matter, which is 

 impossible without entering into the essential peculiarities of 

 animal structure and their relations to the rest of nature, by 

 w : hich they are conditioned and rendered intelligible. However, 

 the results of the preceding investigations have led him to re- 

 lations of affinity w r hose truth will not be granted so long as 

 another system of animals is regarded as perfectly natural and 

 true. Hence, as a corner-stone to the preceding treatises, it 

 seems advisable to attempt a clearing up of the so-called affi- 

 nities of animals. (p. 731, 732.) 



If we take any one of the principal forms of invertebrate ani- 

 mals, we find it in many stages of development, and descending in 

 a more or less uninterrupted series down to the Protozoa. Even 

 the vital characteristics which are manifested in the higher 

 grades, are indicated in their first commencement. The elon- 

 gated Vibriones, the prototypes of the Naidae and Nematoid 

 Worms, and with these of the Insects, are distinguished by their 

 swift and uninterrupted movements beyond all other Infusoria. 

 We must, however, take care not to confound the Bacillaria, 

 which to us appear to be true plants, with the Vibriones. The 

 Paramacia, prototypes of the Trematoda, shorter and broader 



SC1EN. MEM. Nat. Hist. VOL. I. PART II. 12 



