June 5, 1914] 



SCIENCE 



833 



was made in 1908 and had been standing un- 

 changed since that time. A general new cul- 

 ture of rotifers was made from these fertilized 

 eggs and then a few females were selected at 

 random and fed upon a continuous diet of the 

 colorless Polytoma in watch glasses. After a 

 few generations a very high percentage of 

 females were produced. At this period adult 

 females were taken from several of the watch 

 glasses and placed in some filtered water from 

 a jar in which a general culture of rotifers 

 were thriving. Then there was added to this 

 culture water the green flagellate, Dunaliella. 



ous diet of Polyioma to a diet of the green 

 Dunaliella. 



Several other green flagellates have been 

 reared and used as food, but they do not aeem 

 to be effective in causing males to be produced. 

 Many other observations are being made in 

 a further study of the problem, and the de- 

 tailed results together with the exact methods 

 used will be published in a later paper. 



D. D. Whitney 



Biological Laboeatory, 

 Wesleyan Univeesity, 



MiDDLETOWN, CONN. 



The controls were also placed in this filtered 

 culture water and the colorless flagellate Poly- 

 toma was added. 



The above table giving the details of two 

 experiments shows the decided and striking 

 results obtained. The continuous diet of 

 Polytoma caused the adult females to produce 

 6 + per cent., as an average, of daughters that 

 were male-producers, while the diet of the 

 green Dunaliella that was given to the other 

 adult females caused them to produce as an 

 average 79 -|- per cent, of daughters that were 

 male-producers. 



These experiments are not exceptional, but 

 are only two from many others already com- 

 pleted that are equally as good as these and 

 which were obtained in a series of successive 

 experiments. In all other experiments during 

 the last eight years on Hydatina senta there 

 has occurred from time to time a sudden pro- 

 duction of males, but such experiments never 

 could be repeated with equal success. Now 

 the male-producing females can be caused to 

 appear at any time from any stock in the lab- 

 oratory by the sudden change from a eontinu- 



3 Females which produce male offspring. 



THE AMEBICAN PEILOSOPEICAL SOCIETY 



The annual general meeting of the American 

 Philosophical Society was held in the rooms of the 

 society in Philadelphia, AprO 23 to 25 inclusive, 

 and constituted a most interesting series of ses- 

 sions. There was a large number of papers pre- 

 sented, their general character being of a high 

 order of merit and the scope of subjects included 

 being wide. 



The meeting was opened on Thursday after- 

 noon, President W. W. Keen, LL.D., in the chair, 

 when the following papers were read: 



The Physical Cause of the Vnsymmetrical Equi- 

 librium of the Earth Between the Land and 

 Water Hemispheres, with a Theorem on the At- 

 traction of the Terrestrial Spheroid: T. J. J. 

 See. 



Some Observations on the Psychology of Juries 

 and Jurors: Patterson Du Bois, Esq. 



Factors of Influence in the Origin and Circulation 

 of the Cerebrospinal Fluid: Charles H. 

 Frazieb. 



Aspects and Methods of the Study of the Mechan- 

 ism of the Heart Beats: Alfred E. Cohn. (In- 

 troduced by Dr. Keen.) 



