HISTORY OF CHROMOSOMAL VESICLES IN FUNDULUS. 251 



in these crosses where the chromosomes in the two differ. Ex- 

 periments in four series with controls were therefore set up, and 

 were treated with long and short exposure to X-rays as follows 

 (adopting the series designations used by the Hertwigs in their 

 radium experiments). Radiation treatment is indicated by r; 

 untreated, or normal eggs and sperm are represented by n. 



Controls. nF$ X nCc? unradiated. 



Series A. nFQ X nCtf radiated after fertilization. 



Series B. nF$ X 



Series C. rF9 X 



Series D.. rF'9 X rCtf. 



In general my observations corroborate those of Miss Morris 

 as to the regular course of the events in the hybridized eggs of 

 Fundulus and Ctenolabms, and I find very little divergence in 

 the behavior of the definitive chromosomes here from that 

 described by Moenkhaus for Fundulus and Menidia crosses. 



In general also, my results are in line with those of the Hert- 

 wigs in their radium experiments as to the injurious effects of 

 the radiation upon the chromatin, shown, for example, in the 

 failure of the egg nucleus in the series C, when strongly radiated, 

 to take part in the development of the egg, as can be determined 

 by the kind of chromosomes present on the spindle. Similarly, 

 strongly radiated sperm chromatin in series B is killed and takes 

 no part in development. 



In the course of the investigation upon the radiated eggs a 

 set of facts was discovered which bear directly upon the ever 

 recurring question of chromosomal continuity, and which seemed 

 to the writer, worth following out. It is the purpose of this 

 paper to set forth those findings, and to show their bearing 

 upon the important problem of cell structure, and to give at 

 this time the results of the radiation experiments only very 

 briefly, leaving them to be presented elsewhere. 



During the early stages of the investigation the material 

 studied was chiefly that which had been radiated, and most of 

 the drawings given are from those slides. Subsequently, how- 

 ever, eggs of Fundulus which were unradiated have been sec- 

 tioned, and studied from the same point of view and the con- 

 ditions ascertained to be exactly the same as far as the formation 



