WHAT IS AN ORGANISM? 169 



student is referred to special treatises on this subject for in- 

 formation regarding the details of the process, but a few- 

 general statements may be of use in forming a correct notion 

 of the nature of organisms in general. 



The typical cell is composed of a mass of protoplasm with a 

 more or less distinct cell-wall, and, generally, a nucleus, very 

 minute in size and escaping resolution into its elements, but 

 giving evidence of performing some very important functions 

 in the cell when examined with the highest powers of the 

 microscope. 



FIG. 43. Agamogenesis by fission. c-g= the several steps in the process of generation from the 

 parent form a to the production of four separate individuals g. 



The Functions of a Metazoal Organism; Generation. In the 

 Metazoa there are three groups of functions, viz., sustenta- 

 tion, generation, and correlation. Generation is the name of 

 the function by which organic individuals are produced, or, as 

 is commonly said, reproduced. 



Agamogenesis. There are three (or, including alternate 

 generation, four) modes of generation. Agamogenesis, of two 



o a a 



FIG. 44. Agamogenesis by budding. Generation in which the parent individual retains its in- 

 tegrity, sending off a young but relatively immature offspring (/) as an external bud. 



kinds, by fission (i) and by budding (2). This mode may be 

 represented diagrammatically by the following series : 



I. In this series the simple parent individual (a) by sub- 

 division into sub-equal parts becomes four separate individu- 

 als (g), each capable of independent existence (Fig. 43). 



II. The second mode of agamogenesis may be represented 

 by the above diagram (Fig. 44). 



Here a modified fission takes place, the original individual 

 retaining its integrity and sending off a bud, which, after 

 partial development, is separated, completely or partially,, 



