■ 22 DAVID H. TENNENT 



to be included in the reconstructed daughter nuclei. In fig. 13, 

 A and B, and fig. 14, A and B, many chromosomes which are 

 lagging in the first division may be seen. In fig. 17, A and B, 

 a continuation of this elimination by a similar process during the 

 third division is shown. 



A further part of my investigation is concerned with the study 

 of the eggs fertilized in sea water of decreased alkalinity. Unfor- 

 tunately I did not obtain eggs in sufficiently late stages of segmen- 

 tation to enable me to give a final statement of the results. Figs. 

 9 and 10 are representative of the anaphases of the first division 

 in Toxopneustes eggs fertilized by Hipponoe sperm in sea water 

 whose alkalinity had been reduced by the addition of acetic acid. 



In all of this material more lagging chromosomes are found 

 and the average number of chromosomes present in the daughter 

 plates is smaller than in eggs fertilized in normal sea water. 



I had hoped to show that a behavior of the chromosomes cor- 

 related with the results of the artificial control of dominance 

 might be demonstrated. Such a correlation would be indicated 

 by the elimination of Hipponoe chromosomes in the Toxopneustes 

 9 X Hipponoe cf cross. 



As the figures show, there is some evidence that such an elimi- 

 nation takes place but the evidence is not sufficient. 



The study of late segmentation stages should determine the 

 question at once. 



DISCUSSION AND COMPARISON WITH RESULTS OF OTHER 



INVESTIGATORS 



The time has not yet come when we may give a satisfactoi-y 

 discussion of the meaning of our facts and make a trustworthy 

 correlation of these with those determined for insects. 



Herbst's ('90) work was valuable in showing the elimination 

 of chromosomes, or rather the failure of the paternal chromo- 

 somes to take part in the activities of mitosis. But Herbst's 

 experiments do not show that a changed environment results in 

 a change in the character of the pluteus. Chemical fertilization 

 would have given, as Herbst shows, maternal plutei. Delayed 

 fertilization of these chemically treated eggs gives plutei of the 



