PROCEEDINGS 
OF THE 
Cambridge Philosophical Society, 
The Effects of Hypertonic Solutions upon the Eggs of Echinus. 
By J. Gray, B.A., King’s College. (Communicated by Mr 
He A, Potts.) 
[Read 28 October 1912.] 
In the Proceedings of this Society for last year, a preliminary 
account was given of the cytology of hybrid eggs obtained from 
the two species Hchinus esculentus and LHchinus acutus. The 
structure of such eggs was given as follows: 
“In the cross esculentus $ x acutus ¥ the mitotic figures of 
the segmenting egg are perfectly normal, and do not differ recog- 
nisably from those of the pure species. In the converse cross 
acutus ~ x esculentus ¢’, however, a striking abnormality is con- 
stantly present in all the eggs examined. Until immediately 
after the dissolution of the nuclear membrane in the first seg- 
mentation division the behaviour is normal, and 38 normal 
chromosomes can be counted. As the spindle is formed, the 
chromosomes become scattered upon it irregularly, and gradually 
become collected in the equatorial plate. During this process it 
is seen that a considerable though variable number of them are 
either swollen up, or more commonly bear vesicles attached to 
their ends and sides. The staining of the vesicles is always less 
intense than that of the chromosomes, and is progressively fainter, 
the more the vesicle is developed, so giving the impression that 
the chromosome has swollen at one point, and that the chromatin 
is thus more thinly diffused in the wall of the vesicle than in the 
normal part of the chromosome. In the equatorial plate stage 
the vesicles may either remain attached to the chromosomes which 
produced them, or become separated from them; those which 
VOL. XVII. PT. 1. I 
