DEVI I.MpMKNT OF EGGS OF ARBACIA AND CH.ETOPTERUS. 275 



the same rate. If the cy>tin had any effect on the segmentation 

 it was too slight to be detected either in the- living eggs or in 

 -erved material. 



On the morning of July 15, both cultures contained many 

 livin^ embryos; those of the control were well-developed t 

 trul.i- that were swimming at the- -urface of the water in a normal 

 manner; those in the cv-tin -olmion were decidedly -mailer than 

 the control larva?, and nio-t of them were -wininiini; at the bot- 

 tom of the dish. Thinv hours after the experiment wa- -tarted 

 all of the larva? in the cystin solution were dead, although the 

 larva- in the control culture were Mill in good condition. I'iv- 

 scrved material showed that the development of tin- eggs that 

 had been subjected to the action of the cystin solution took p! 

 in a perfectly normal manner, although it was somewhat >lo\\er 

 than that of the eggs in the control lot. 



Mathews found that cystin produced a decided acivl< -ration 

 in the development of the eggs of Arbacia, which \\a- apparent 

 from the fourth division on. The solution that In- u-id \\a- 

 made as follows: "One hundred centimeters of -e.i-uater were 

 shaken for a moment with about a centigram <>\ r\ -talline 

 i in and the mixture poured into a linger ln.\\l with the uii- 

 di-solved cystin. The eggs, fertili/ed -omeihin^ K- than an 

 hour before, were then added and tin t\ during d-\i-lop- 



iiifiu .imong the crystals of c>'stin at the boitom ( .| the di-h." 

 A- a solution made in this wa>' i> tindoul.tedK much \\eakcr 

 than that employed in my fir-t exjn riment , it -eenied ]irobal>U- 

 that the opposing results obtained \>\ Matheu - ,md m\ -el! mi-lit 

 be due to the difference in the -iren^th of the -olution^ to which 

 tin -gs were subjected. The experiment \\a^ therefore re- 

 peated \\ilh a different lot of eggs, the -olution of c\>tin that 

 \\a- n-^ed being prepared in the manner described \>\ M.iiheu-. 



In tin's experiment, also, the development of the e^-- appeared 

 to pro^iv-,s at about the same rate in both the c\ -tin culture and 

 in the control. Some of the e-i;- in the cy-iin -olution seemed to 

 Moment much more rapidly than other-, and a very few of them 

 developed at a faster rate than the major portion of the c;^- in 

 the control culture. A careful comparison between the \\\o 

 cultures, made at intervals of about one half hour during the 



