572 CLARENCE E. McCLUNG 



'identical' and 'homogeneous/ as Delia Valle asserts, there 

 would not be the marked difference in behavior of the euchromo- 

 some and the accessory chromosome which we always witness in 

 the Orthoptera. Most especially would this be true where the 

 two types constitute a single mitotic element. What a con- 

 trast the actual facts regarding exactness and differential char- 

 acter of the chromosomes present to the crude and vague gen- 

 eralizations of those who conceive the cell to be only a micro- 

 scopic laboratory for the play of the chemical forces involved in 

 colloidal crystallizations. It is however fortunate that there are 

 minds not content with a half way denial of the facts relating 

 to nuclear constitution and the substitution of indefinite generali- 

 zation about the activity of the cell as a whole or of specific 

 enzymes, etc., but which push the denial of precision of organi- 

 zation to an unconscious reductio ad absiirdum in some field of 

 chemistry. For through this service we are brought to see the 

 contrast between clearly defined facts, gained through re- 

 searches of the most exacting and painstaking character and the 

 uncertain and contradictory theories springing from impatient 

 and prejudiced minds. 



The facts regarding the differential behavior of the chromo- 

 somes, together with those relating to numbers, sizes and forms, 

 are, many of them, now commonplaces of observation and are 

 regularly determined by beginning students in microscopic 

 anatomy. Others, such as those exhibited by the euchromosome 

 multiples described in this paper, are no less striking and sig- 

 nificant. They all speak clearly and unequivocally in favor of 

 an order, in terms of morphology, and against one of a more 

 remote and molecular character. But no single feature of 

 chromosome behavior possesses the significance and fundamental 

 importance which attaches to the unquestioned reproduction of 

 each individual chromosome during mitosis. Why, unless there 

 be something in the organization to be preserved, should the 

 elements so carefully reproduce themselves down to the most 

 minute structural pecuharities? It is inconceivable that the 

 complexity and exactness of this process should exist unless there 

 is some correspondingly important function to be carried out. 



