252 A. RICHARDS. 



of the chromosomal vesicles and their history is concerned. I 

 wish to emphasize that neither the fact of the hybridization in 

 the Fundulus 9 X Ctenolabrus d" crosses -nor the exposure to 

 the X-radiation is responsible for the conditions here figured, 

 for a full set of figures from normal Fundulus eggs in addition to 

 those here presented could easily have been made and exactly 

 the same conditions depicted, had the differences been thought 

 to warrant the extra effort and time. To neither of these two 

 experimental factors can the conditions here described be 

 attributed. 



It is quite possible and indeed the writer inclines to this 

 opinion, that the treatment with X-rays serves to emphasize the 

 vesicular condition of the chromosomes to make more clear 

 relationships which undoubtedly already existed. Miss Caro- 

 thers finds that X-ray treatment tends to increase the ease 

 with which she finds chromatin granules in the peculiar vesicular 

 condition which she calls "chromosomal vesicles." 1 It is possible 

 that the fact that I first studied the radiated material is ac- 

 countable for the recognition of the conditions here, although 

 having once worked out the facts there I had no trouble in veri- 

 fying the observations in normal untreated and uncrossed 

 Fundulus eggs. Many of the findings have been confirmed by 

 Miss Pinney in a study of Fundulus eggs as yet unpublished, 

 and I have demonstrated my slides to various workers at Woods 

 Hole, none of whom had any difficulty in seeing the conditions 

 here described. 



This account offers a rather different history of chromosome 

 behavior from that usually given. The transition stages from 

 one step to another are very clear, however, and do not usually 

 permit of any other interpretation, so far as the writer can see, 

 than the one here set forth. The new account of chromosomal 

 formation and processes connected therewith, it will be seen, is 

 easily fitted into the orthodox interpretation without doing 

 violence to any important conception of mitotic behavior. It is 



1 This use of the term is unfortunate in the light of its earlier application in the 

 sense used throughout this paper. "Chromosomal vesicle" in the sense of Sutton 

 and Conklin refers to a vesicular condition of the whole chromosome. Miss 

 Carothers has subsequently pointed out that the structure she described is in reality 

 a plasmosome vesicle. (Jour, of Morph., 28, p. 465, 1917.) 



