PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 349 



size of fibre, a common or homologous central ending in brain 

 or cord, and a uniform embryological origin of its ganglia, — 

 a series of facts justifying the term "functional systems" as ap- 

 plied to nerve components and placing the stamp of approval on 

 this mode of nerve analysis. 



PROTOZOOLOGY 



In 1675 Leeuwenhoek discovered the protozoa ; and from that 

 time to this the group has held a firm grip on the scientific 

 imagination. Aside from their own inherent beauty, the protozoa 

 gain an additional interest as the natural starting point for the 

 evolutionary study alike of physiology and of morphology in the 

 higher animals. The structure of the protozoan cell gives light 

 on the metazoan cell with its more highly specialized nuclear 

 structure ; physiological processes are reduced to their lowest 

 terms in the protozoa ; the simple tropisms and other reactions 

 of the protozoa may give the clue to the voluntary and con- 

 .scious psychical activities of the higher animals; in the conjuga- 

 tion of the protozoa we cannot fail to recognize the prototype 

 of the sexual reproduction of the metazoa, complicated in the 

 latter by the sharp separation of somatic and germ cells. It is 

 not surprising that an enormous protozoological literature has 

 sprung up in the last few years, the annual bibliography literally 

 running into the thousands of titles ; in one, at least, of our 

 universities an independent professorship of protozoology has 

 existed for nearly ten years. 



Let us consider briefly one phase of the discussion of pro- 

 tozoan reproduction. W'eismann, during the eighties, had com- 

 pared the unicellular organisms with the germ cells of the higher 

 forms. While the mass of cells forming the soma or body of 

 a metazoan has a somewhat definite length of life and then, 

 accidents aside, dies a natural death, the germ cells continue as 

 an unbroken series from generation to generation throughout the 

 existence of the species. On the other hand, the protozoan shows 

 no distinction of soma and germ : when division takes place, the 

 new individuals formed are, in one sense, as old as the species. 

 in another, newly born and, according to Weismann, provided 



