162 THE AMERICAN MONTHLY [September, 



answer grave problems of philosophy, to render possible brilliant discoveries, 

 if not a brilliant scientific epoch. To these sentiments is due our knowledge 

 of and interest in the Protozoa. 



The animal kingdom' is divided into two natural groups or series — the 

 Protozoa and the Metazoa. The former includes the unicellular forms or 

 those generally regarded as the equivalent of the histological cell ; the latter 

 are multicellular, their tissues are composed of histogenetic elements or cells, 

 and these are arranged in two sets, viz., the ectoderm, or outside body-wall, 

 and the endoderm, or lining of the alimentary cavity. These commence ex- 

 istence as a nucleated cell ; their subsequent growth and complexity are the 

 result of cell multiplication and modification mingled with the products of 

 cell life. The Protozoa do not pass beyond the primitive stage, /. e., cell 

 division giving rise to individuals. None are modified for the sake of others, 

 and all perform similar functions and all the essential functions of an animal. 

 Truly, then, we have here the simplest forms of animal existence possible, 

 whilst the life of the metazoon may be regarded as the resultant of hosts of 

 individuals comprising it and among which division of labor is fully carried 

 out ; on the other hand in the protozoon we see manifested by each individual 

 onl}' the capabilities of one element. In this case, then, we deal with the ab- 

 solute elements and not with resultants. Here the mystery of mysteries 

 seems to be almost unveiled. The nature of life, if it is to be revealed by 

 the study of organisms which exhibit it, should appear from the study of the 

 naked, disassociated protoplasmic atoms in which all the essential attributes 

 of life are manifested. The simplest of these, for they differ widely among 

 themselves.are without nerves ; yet they are sensitive — they are without organs ; 

 yet they move about freely, gather, select, and digest their food, and escape 

 from their enemies ; they reproduce their kind, and maintain themselves when 

 subjected to unfavorable conditions with as great certainty as do the complex 

 and bulky animals. In short, their life histories, as we get to know them 

 better, prove to be as definite, the specific characters as constant. But does 

 the clearer understanding of these forms in their simplicity shed light on the 

 nature and origin of life which are held by many savants not to be trans- 

 cendental ? It seems to me not, and that we are still very far from the solu- 

 tion of these great problems. The most that has eventuated thus far is a 

 shifting of the point of view. This has undoubtedly afforded a clearer sight ; 

 but the perfect is not revealed. Still, whilst the object sought may be illu- 

 sive, and, as one who pursues the rainbow finds it ever a few steps beyond 

 his reach, so here, the answers to the questions mentioned, which have been 

 so eagerly sought for in the bodies of the simplest and beginning forms of 

 life, ever elude the microscope and reagents of the inquirer. Then are we 

 no nearer an understanding of these matters than before.'' Most certainly we 

 are. The problems of human society are not nearly all solved, but there hav-^ 

 been tremendous strides in advance since the individual has been made t'^*^ 

 object of consideration rather than communities. Although the results ^^' 

 tained are so far short of hopes and expectations, yet,' in the prosecutic^^ '^^ 

 these inquiries in connection with Protozoa there are fascination and interest. 

 Further than this their infinite variety, their gracefulness of form and ir ^tions, 

 their ubiquity and high endowments, coupled with simplicity, firmly bold tiie 

 attention of the student. 



For the sake of clearness in the subsequent parts of this discourse let us 

 attend for a few minutes to the organisms themselves and the terms designat- 

 ing the parts. (To aid in this explanation simple figures were dra wn on the 

 black-board.) 



A cursory survey will disclose the fact that there exist very gre?^t differences 

 among those creatures comprehended in Protozoa, The reach ^^I'oi^i the low- 



