May 24, 1907] 



SCIENCE 



823 



Eesult of Conjugation,' by Sara White Cull. 

 Experiments were made to determine (a) 

 whether conjugation always produces rejuve- 

 nescence and (b) whether the fertilization 

 resulting from conjugation is or is not mutual. 

 Conjugating pairs of Paramecium caudatum 

 were isolated and the individuals, after they 

 had been separated, were isolated and counted 

 at intervals for a month. The statistics 

 gathered show that (a) conjugation frequently 

 fails to produce rejuvenescence in either con- 

 jugant and (b) that conjugation, among the 

 infusoria, is not mutual and there are strong 

 indications that it is incipient fertilization as 

 seen among higher forms. ' Artificial Par- 

 thenogenesis in Thalassema mellita,' by 

 George Lefevre. An investigation of artificial 

 parthenogenesis in Thalassema mellita has 

 shown that the unfertilized eggs of this worm 

 can be induced to develop into actively swim- 

 ming troehophores by immersion for a few 

 minutes in very dilute solutions of both in- 

 organic and organic acids. Nitric, hydro- 

 chloric, sulphuric, carbonic, acetic and oxalic 

 acids were used successfully, and in favorable 

 experiments 50-60 per cent, of the eggs de- 

 veloped into swimming larvae that were hardly 

 distinguishable from normal troehophores of a 

 corresponding stage. The parthenogenetic de- 

 velopment in many cases involves a perfectly 

 normal maturation, a more or less regular 

 cleavage, and the usual processes of differ- 

 entiation leading up to the formation of the 

 normal larva. The reduced number of chro- 

 mosomes (twelve) persists when the matura- 

 ' tion has been normal, and has been repeatedly 

 counted even in late blastula and gastrula 

 stages. Differentiation of the egg does not 

 occur in the absence of cleavage, and all 

 ciliated bodies, whether normal or abnormal, 

 possess a cellular structure. ' Concerning the 

 Theory of Tropisms,' by Jacques Loeb. ' The 

 Mechanism of the Galvanotropic Orientation 

 in Volvox,' by Frank W. Bancroft. O. P. 

 Terry's result, showing that volvox colonies 

 subjected to a bright light swim to the cathode, 

 while those subjected to a dim light or dark- 

 ness swim to the anode was confirmed. This 

 difference was found to be due to a reversal of 



the pole at which the galvanic current acts. 

 In anodic colonies the galvanic current stops 

 the fiagella current on the anode side of the 

 organism. In cathodic colonies the orienta- 

 tion is produced by stopping the fiagella cur- 

 rent on the cathodal side. Pressure on anodal 

 colonies reverses the pole at which the gal- 

 vanic current produces its effect. 



SOCIETIES AND ACADEMIES 

 THE PHILOSOPHICAL SOCIETY OP WASHINGTON 



The 633d meeting was held on April 13, 

 President Hayford in the chair. 



Professor Newcomb discussed the question 

 of the variability of the sun's radiation, giving 

 the results of a statistical investigation on 

 that subject. The line of investigation was 

 directed upon the point whether there is any 

 tendency to synchronism between spells of 

 high and low temperature in widely separated 

 regions of the earth. The material included 

 annual mean temperatures, as observed from 

 1820 to 1904, and deviations during terms of 

 ten days, and of one month, from 1872 until 

 1904. The general conclusion was that there 

 were no well-marked deviations other than 

 those which resulted from local causes, and 

 that when these were duly allowed for, the 

 temperature of the earth at large remained 

 constant within a fraction of a degree. The 

 only appreciable indication of any cosmical 

 cause affecting the whole earth was in the 

 monthly deviations. So far as the investiga- 

 tion had been carried, these indicated that 

 there really was a deviation, which could be 

 accounted for by a change in the sun's radia- 

 tion from month to month, sufficient to change 

 the temperature of the equatorial regions by 

 an average amount of about one third of a 

 degree centigrade. But even this small 

 change may be due to the trade winds and 

 other great movements of the air, by which 

 a body of air colder or warmer than the 

 -normal is carried from one region to another 

 within the monthly limits. The only ascer- 

 tained law of change was that of the sun- 

 spot period. The result reached by Koppen, 

 that the temperature of the earth generally 

 was somewhat higher the fewer the sun-spots, 



