34 THE AMEEICAN MONTHLY [February, 



'•'■ primary formative matter," and Beale's designation of it, bioplasm, 

 more definitely expresses the idea of its being a h'fe plasma. 



In Nitella, Valisneria, or Anacharis you may seethe colorless current 

 circling in every cell, building and unbuilding with a chemistry bevond 

 our ken, and in all the iu'gher animals it seems to be the matrix in 

 wdiich are fashioned the tissues and the bones, the souixe also of the 

 contractility of the muscles and the sensibility of the nerves. In your 

 own warm blood you will find protoplasm, in the form of the ^' white 

 corpuscles." 



Animal or Vegetable ? — How are we to tell whether the diatom 

 is animal or vegetable? Here is another of these points at which ig- 

 norance has been accustomed to think itself wise, but where wisdom 

 has come to admit itself ignorant. Prof. Huxley set forth the situation 

 of this matter most admirably in his lecture entitled " The Border 

 Territory between the Animal and the Vegetable Kingdoms," and there 

 has been no essential change in the case since he therein stated it. 

 Naturalists had been in the habit, from the days of Cuvier, of relying 

 upon four proofs which they considered conclusive of the animal nature 

 of any organism. Tliese were (i) the possession of an alimentarv 

 cavity, (2) the presence of muscles for locomotion and of nerves for 

 sensibility, (3) the existence of nitrogen as a constituent element of the 

 body-substance, and (4) the exercise of the function of respiration — • 

 the absorption of oxygen and the exhalation of carbonic acid. But all 

 of these distinctions have been shown to be subject to so manv excep- 

 tions as to destroy their value as tests. 



The difficulty with this matter, as well as with the subject of vitality, 

 is that we look for single distinguishing signs when we ought to take 

 into consideration a whole series of phenomena at once. Thus life 

 would prove to be not an entity, an essence, or even a principle, but 

 rather a process. In like manner, the criterion of animal life, as dis- 

 tinguished from vegetable, would not be found in assimilation, sensa- 

 tion, self-motion, or any other one thing, but in a group of actions and 

 attributes, by their sum-total turning the scale to the animal side. 



As far as we know, the diatom protoplasm has no proclivity for can- 

 nil)alism, as all animal protoplasms seem to have. Taking this nega- 

 tive quality for what it is worth, and adding it to the general sum of 

 the diatom's other characteristics which common sense somehow 

 recognizes as belonging to the vegetable kingdom, we arrive at a 

 decision that the object of our consideration is a plant and not an 

 animal. 



Classification. — Having made up our minds that diatoms lie within 

 the boundaries of the vegetable kingdom, we shall have no difficulty 

 in referring them to that sub-kingdom which includes all non-vascular, 

 or, in other words, leafless and rootless plants — called thaUopJiyta'. 

 In this sub-kingdom is the well-known class Algcv^ which embraces all 

 aquatic thallophytes, and to which therefore the diatoms must belong. 

 Indeed, they constitute a very important sab-class of algaj, which derives 

 its name from them — the diatoinacece . 



The diatomacete themselves get their name from the Greek word 

 ihaTii;j.<i^\ which means <-?/■/ tJn-ough^ cut in izvo, or cut zip, and which 

 was applied to them with reference to the bead-like manner in which 

 tlie individuals of many genera cling togetlier in fragile strings. 



