148 



THE MICROSCOPE. 



DIATOMACE.E. 



Among the organic beings, whose existence the microscope has 

 revealed, few possess a higher interest than the group of Infusoria now 

 known as Diatomacece, or Brittleworts. Appearing every where as the 



fig. 96. Skeletons of Diatomacece. 



Gomphonema capitatum and elongatum ; Diatoma vulgare ; Achnanthidum lineare, 

 and coarelatum ; Amphitetras antediluviana, front view ; Orthosira spinosa, front 

 view ; with globular and oval forms, found at Springfield, Barbadoes. 



first-born of life, and wherever inorganic matter is found in a condition 

 fit for their development, and being provided with a siliceous shell, 

 their forms remain unchanged from the remotest periods of this world's 

 history. Recent specimens are of a green colour, with a tinge of 

 brown ; in form generally that of a prism, or four-sided ; and their 

 flinty remains consist of one or more pieces, the delicate lines of which, 

 and the fineness of their tracing, set at defiance the most wonderful 

 efforts of imitation. They are found abundantly, both in the inland 

 waters and the ocean, often carried through the air as particles of fine 

 dust. The earliest observers considered them to be animals, undoubt- 

 edly; and animals they were decidedly pronounced by Ehrenberg. 

 Later investigators have declared them to belong to vegetables. I be- 

 lieve, with Kutzing and others, that they are rightly placed by Ehren- 

 berg among the earliest forms of animal life. During my examina- 

 tions of the ciliary motion in the Desmidiacece, near the end of the 



