1892.] MICROSCOPICAL JOURNAL. 233 



The Protozoa — a Phyluiu of the Animal Kingdom Considered 

 Biologically.* 



By H. L. OSBORN, 



HAMLTNE, MINN. 



[with frontispiece.] 



It would seem very remarkable indeed, if we were not now 

 used to the conception, that there are so few different kinds of ele- 

 mentary substances and so few different elementary principles. 

 The early mind looked on all observed differences as radical and 

 indicative of fundamental and essential unlikeness in things ob- 

 served. This quality of mind persists to-day in rudimentary peo- 

 ples and in the untaught and unobservant of more advanced races. 

 But the person who lives in the light of the present era ot scien- 

 tific thought expects that the complex will upon inspection resolve 

 itself into the simpler and finally into the simple. If we examine 

 any single member of the higher groups of animals or plants, we 

 fintl that, complex though they may be, their actions are the alge- 

 liraic total of the powers of the multitudes of cells which compose 

 them. Cell growth and reproduction, tissue work, division of 

 labor, comprehend activities in plants or animals which in tlie 

 total we speak of or think of as the creature's life. 



Side by side with this idea of the biologv of an animal or plant 

 as the sum of the activities of component similar cells or really 

 prior to it at the outset, though of slower growth, is the comple- 

 mentary conception which sees groups of animals or plants as the 

 natural descendants of prior forms. This idea has long been 

 struggling for existence in the world of beliefs, and cannot yet be 

 said to have gained a permanent place among the concepts of the 

 laity, though it is fully accepted by most professed biologists. 

 Looked at collectively the different kinds of animals appear to be 

 serial ; that is, they are not isolated and imlike, but are more or 

 less closely similar. The grades of similarity are somewhat par- 

 allel in different series. The groups that have been formed by the 

 study of animals includes phyla the most comprehensive and 

 classes, orders, families, genera, species, and varieties, named in 

 their lessening order. Each of these groups has a name and very 

 often the name we use in speaking of an animal is the name of its 

 order or class, not of its exact genus or species. Thus we speak 

 of the moth or fly or bee. In this way the same animal may be 

 called by several different appellations, and we may speak of the 



* For the benefit of any readers who may care to look up the Protozoa more fully than the 

 limits of this article permit, I append a few titles of works mostly easily accessible : 



1. Kncyc. Britt. Art. Foraminifera. Carpenter. 



2. " " Art. Protozoa. Lankester. 



3. Kent. Manual of the Infusoria. 



4. Stokes. Infusoria of the United States. 



5. Huxley. Anatomy of the Invertebrata. 



6. Parker. Elementary Biology. 



7. Leidy. Fresh-water Rhizopoda. 



8. Haeckel. The Radiolaria. 



The article Protozoa, by E. R. Lankaster, in Encyc. Britt., contains a very good bibliograph- 

 ical index at its close. 



