1902.] NATURAL SCIENCES OF PHILADELPHIA. 211 



The organizatiou being then one closely united whole, we reach 

 the principle that the organization as a whole must be studied ; and 

 hence that any scheme of classification based upon one kind of 

 organs alone is erroneous in its method.^" The truth of this is fur- 

 ther borne out by the following reasoning : The organization being 

 one closely connected whole, there is a perfect physiological and mor- 

 phological correlation of its parts ; and although some of them have 

 a greater value to the whole economy than others, yet each part is 

 dependent upon the others. The parts are not individuals, in the 

 sense in which the individual has been defined (Section II), since 

 they are normally incapable of separate existence. ^^ When we say 

 ' ' a gland cell of the intestine of a snail, ' ' we speak in succession of 

 a part of a larger part of a whole. Not only from physiological 

 facts does this correlation become apparent but from morphological 

 as well, for none of the parts show sharp demarkatious. A vertebra 

 of an adult mammal might be considered at first as a well circum- 

 scribed part; yet besides being one of a series of vertebrai, all 

 developed from one anlage, its fibrous sheath passes over gradually 

 into the tendons of the muscles attached to it, and its nerves and 

 blood vessels are mere portions of the nervous and vascular systems 

 of the whole organization. Similarly with a limb, a sense-organ, a 

 limg, etc. For none of the parts of the whole organization can 

 sharp boundaries be found ; even the cells are either connected by a 

 fusion of their contiguous membranes or processes, or by a common 

 intercellular substance. '" 



The parts of the organization are then not individuals, since 

 between all the parts exists the closest correlation ; and the ' ' largest 

 disconnected whole ' ' is the organism of phylogeny. Further, no 

 part can be understood alone by itself, but the place which it occu- 

 pies in the whole organization must be considered. 



It is not to be wondered at that the paits of organisms are not 



'"A case in point is Huxley's brilliant paper On the Classification of 

 Birds, 1867, wherein birds are primarily grouped according to the 

 structural characters of one region of the skull. 



" The germ cells, however, in their mature stages come under a dif- 

 ferent point of view, for they are then individuals of a second generation 

 which have not yet left the body of the first. In tlie present discussion, 

 wlien not otherwise stated, only the somatic parts are considered. 



''^ The migratory cells of the body of Metazoa show perhaps more uule 

 pendence than the other cells, yet they too are iutluenccd by the state of 

 the organism as a whole ; and even such blood and lymph cells are 

 normally incapable of existence outside of the organism. 



