168 INTRODUCTION TO CYTOLOGY 



of this beyond the organism to the group and the means for it in the phenomena 

 of maturation and fertilization are easily established by observation; the age 

 old existence of all these circumstances is revealed by the near approach to 

 uniformity in the chromosome complex of the multitude of species of unnumbered 

 individuals constituting a family. And yet, in the face of this overwhelming 

 mass of evidence indicative of order, system and specific chromosome organiza- 

 tion, some conceive only the action of ordinary chemical forces, or the chance 

 association of indifferent substances, while others, over impressed with the 

 thought of a general coordinating force in the organism, deny significance to the 

 orderly play of its cellular parts." 



"It is my belief that the observed act of reproduction, by which the organiza- 

 tion of the chromosomes is materially transmitted in each mitosis, together 

 with all facts indicating extensive distribution of given conditions, definiteness 

 of organization, uniformity of behavior and consistence of deviation from the 

 normal, are so many clear indications of the individual character of the chromo- 

 somes. Transmutation of form, even to an extreme degree, can not be held as a 

 valid argument against a persistent individuality. A consideration of the criteria 

 applied to larger organic aggregates well supports this view. Such objects are 

 said to possess individuality when they exhibit a more or less definite unity which 

 is persistent and characterized by peculiarities of form and function. Most 

 clearly defined is this individuality when it may be perpetuated through some 

 form of reproduction to find expression in new units of similar character. The 

 term does not connote unchangeability, and there may be fusions with more or 

 less loss of physical delimitations, followed by separation, even after exchange 

 of substances. The test of individuality is material continuity, but it does not 

 necessarily involve complete or entirely persistent contiguity. 1 An organism may 

 bud off new individuals similar to itself, the substance of its body differs from 

 time to time, movements of parts take place, fragmentation occurs, extreme 

 attenuation or extension of substance is found, even separation and recombina- 

 tion of parts may happen and yet the individual maintains itself. What it may 

 have been in the past, what its possibilities of future development are, what 

 potentialities of multiplied individuality it suppresses do not affect the reality of 

 its individuality. It is, as Huxley says, 'a single thing of a given kind.' If 

 one such thing divides into two, there are two individuals; if two unite into one 

 indistinguishably there is a single individual; if a fusion of two things occurs in 

 part, without loss of physical configuration, there are still two individuals in 

 existence. Only when the substance of one thing disappears or becomes in- 

 corporated integrally into the organization of another does its individuality 

 depart. 



If all these variations of physical state may occur in the history of an organism 

 without sacrifice of individuality, there can be no reason for urging them against 

 a conception of the individuality of the self-perpetuating chromosomes." 



Bibliography 8 



Somatic Mitosis. Individuality of Chromosomes 



Agar, W. E. 1912. Transverse segmentation and internal differentiation of 

 chromosomes. Quar. Jour. Micr. Sci. 58: 285-298. pis. 12, 13. 

 1 Italics ours. 



