1902,] NATURAL SCIENCES OF rillLADEEPHIA. 197 



pared, unicellular with multicellular, and intracellular with inter- 

 cellular. In other words, we might say that it is not the cells which 

 make the organism, but the organism which makes the cells. This 

 thought maybe carried further: the cell contains particular parts 

 or elements, such as chromosomes, centrosomes and cytoplasm, but 

 is more than a mere aggregate of these; and the Annelidau organi- 

 zation contains parts, such as the metameres, but the latter are not 

 separate organisms. Thus the Metazoan is not a mere symbiotic 

 aggregate of cells regarded as individual organisms, but these cells 

 are merely subservient parts of the whole organization. Under 

 " organism " then we must consider the whole organization, if we 

 would not confuse entities of different values; and for the parts of 

 such organisms the terms ' ' structural element " or " micro- 

 organism." 



The organization as a whole is, then, of primary importance, not 

 its elements. And by employing ' ' organism ' ' to mean the 

 " organization as a whole," we are justified in classing " organ- 

 ism" as synonymous with " individual," as defined above, namely, 

 ' ' the largest disassociated whole. " It is the organism defined in 

 this sense that is the unit to be treated in phylogenetic classification. 

 It is necessary to be clear upon this point, and not to regard parts 

 of cells, or cells, or tissues, or organs as the primary materials to be 

 treated in classification. The organisms or individuals of our 

 classification are then primarily the kind which are mentally 

 grouped under what we generally understand as "species." And 

 since a species is simply a mental association of similar individuals 

 or organisms, it cannot be perceived ; so that species are not the 

 materials for classification, but the perceptible individuals or organ- 

 isms which compose them. 



This conclusion as to what are the organic units primarily to be 

 classified is further emphasized when we come to consider at what 

 stage of its life-history the organism should be classified. The 

 organism may be treated at any or all stages of its cycle, in order 

 to understand its structure and growth phenomena ; but it must be 

 determined at what stage it is to be classified, in order to sliow its 

 phyletic progress. 



Now classification must represent not only similarities of descent, 

 but divergence from the original ancestor ; must show how far each 

 organism has progressed in its evolution. The stage at which it is 



