OF ANIMALCULES. JO 



rolls eels a distinct species from the viviparous, but this 

 has not been demonstrated ; and I fear microscopic na- 

 turalists have too often divided animalcules into distinct 

 species which merely differ in the stage of their growth, 

 thus unnecessarily augmenting the number of names, 

 and creating confusion ; for, surely, if there only existed 

 half the number of species that are well known as dis- 

 tinct, they alone would be fully sufficient to engage the 

 constant attention of any lover of the works of creation, 

 in exploring their structure and economy. It is, how- 

 ever, but common justice to the microscopist to men- 

 tion, that, although labouring under such immense dis- 

 advantages in this department of nature, from the mi- 

 nuteness of his subject, the difficulty of preserving iden- 

 tical specimens from infancy to maturity, and even if he 

 accomplishes this satisfactorily, all his knowledge of them 

 is obtained by one organ only — the eye — and that in an 

 artificial manner, while ornithologists have committed 

 more egregious errors. Thus Gmelin, and some others, 

 have described the same individual, '' the Golden Eagle," 

 {Aquila chrt/s'detos), indifferent stages of its growth, as 

 four distinct species. 



126. Y iBRio Jluviatilis, The fresh ivater microscopic Eels, 

 — These animalcules, which are found in different vege- 

 table infusions, and especially in river water, near the 

 surface, are smaller and more pellucid than the former. 

 Little of their internal organization is known ; but what 

 is ascertained, agrees so much with the paste eels that 

 it is unnecessary to repeat it. 



