1892.] NEW-YORK MICROSCOPICAL SOCIETY, 11 



elusion of philosophy. The reason of course is that philosophy- 

 has assumed false premises. There is in fact no one protoplasm 

 ascertained to be common to all living things. The latest science 

 proves conclusively that what Huxley laid stress upon as the 

 physical basis of life, and Beale staked his theory of " vital 

 power" upon, as the true " germinal matter," are not structure- 

 less colloids, alike wherever found, but that they are complex in 

 structure and various in chemical composition, — in short, that 

 there are probably as many different protoplasms as there are 

 organisms. 



How, then, are we to tell whether our diatom is animal or vege- 

 table ? Here is another of those points at which ignorance 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 Ter- 

 ritory 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 re- 

 lying upon four proofs which they considered conclusive of the 

 animal nature of any organism. These were (i) the possession of 

 an alimentary 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 many exceptions as to destroy 

 their value as tests. For example, the reproductive bodies set 

 free by certain algge, which, from their resemblance to animals, 

 have been given the name zoospores, are as active in their move- 

 ments as any animalcules, and to all appearances exercise quite 

 as much volition. They also appear to search for food and are 

 provided with internal spaces which Ehrenberg, not altogether 

 unreasonably, took to be stomachs, and upon the existence of 

 which he founded his family of the polygastrica, a division of the 

 animal kingdom in which he included, with numerous zoospores, 

 not only true animalcules but also all diatoms. It is not yet cer- 

 tain that zoospores are really destitute of a digestive system, and, 

 as to muscles and nerves, they are certainly as well endowed as 

 are the lowest known animals. On the other hand, many para- 



