HISTORY OF CHROMOSOMAL VESICLES IN FUNDULUS. 2/5 



on the whole, been futile. It is, therefore, an abuse of language 

 to speak of a persistent individuality of the chromosome." 



There is, however, a great mass of evidence in favor of a 

 view of chromosome individuality or rather, since there is so 

 little evidence of actual chromosome persistence as unchanging 

 and identical bodies during the resting stage, the hypothesis of 

 genetic continuity of chromosomes. The fact that almost in- 

 variably the same number of chromosomes emerges from the 

 resting nucleus that went into it, Boveri's studies of abnormal 

 variations in the early development of Ascaris eggs, Zur Strassen's 

 observations of the giant embryos of Ascaris, the previously men- 

 tioned discoveries of the independence of maternal and paternal 

 chromatin in hybrid eggs, the constant recurrence of chromosomes 

 in the same form and even position, e. g., in root tip cells of Yucca 

 (Clemens M tiller) and in Ascaris eggs (Boveri), their gradation in 

 size invariably repeated in certain insect germ cells, the history 

 now well known of the accessory chromosome, which retains its 

 identity from one cell generation to the next, the recent studies 

 which have shown clearly the homologies of chromosomes other 

 than the accessory as well as their independent behavior, and 

 finally the correlation of the results of recent studies in genetics 

 with such a behavior on the part of the chromosomes, all these 

 points constitute strong inferential evidence in favor of a theory 

 of chromosome continuity. 



Chromosome continuity is a theory as applied to resting 

 nuclei only. In the mitotic stages the facts are clear; the 

 chromosomes are distinct bodies which behave as units and it is a 

 general observation that those of one cell are homologous with 

 those of others in the same organs and in general in the same spe- 

 cies. It is only in the interkinesis that the facts partake in any 

 way of the nature of a hypothesis and admit of differences of 

 interpretation regarding the point here discussed. In this state 

 it is difficult or impossible to recognize chromosomes as distinct 

 entities and accounts which seek to distinguish them throughout 

 rest have been and must be received with great caution. Adverse 

 criticism's of the theory have been based upon claims of faulty 

 technique, faulty observation, upon obvious objections to a hy- 

 pothesis of strict individuality (which is impossible both in a 



