518 



SCIENCE 



[Vol. LVI, No. 1453 



the close of the telophase and closing with the 

 first tendency towards the formation of the 

 spireme or, in other words, to the so-called 

 resting condition. 



E. Haeekel described such a process of 

 growth as the perigenesis of the plastidules 

 though perigenesis as described by Haeekel is 

 not referred to by MuUer. 



The sporophyte cell, from the end of the 

 telophase to the beginning of the next pro- 

 phase, would therefore become, normally, a 

 tetraploid unit with the chromatic contents 

 merely in need of distribution in the ease of 

 the vegetative division or, in the case of the 

 reduction division, of random segregation. 

 Actual return to the gametophytic condition is 

 not accomplished till the sec-ond division since 

 dyads are separated on the first or so-called 

 heterotypic spindle. 



It is assiimed that the genes after the genesis 

 of their like, reassemble in such a fashion that 

 they form a continuous prophase spireme 

 thread. It is during this reassembling of the 

 genes, this reorganization of the nucleus, that 

 the phenomena of crossing over may occur as 

 well as perhaps some mutations not due Ito 

 such factors as non-disjunction, re-duplieatlon, 

 deficiency, etc. 



My material was examined in the living con- 

 dition, by special staining methods of the 

 living cells in sugar suspensions, by intra- 

 vitam staining, and, as a check, by the standard 

 fixing, hardening, and imbedding methods. 



Detailed descriptions, drawings, and photo- 

 graphs will be published in the near fuiture. 

 Harold C. Sands 



Columbia Universitt 



THE AMERICAN CHEMICAL 

 SOCIETY 



(Continued) 



DIVISION OF RUBBER CHEMISTRY 



C. W. Bedford, chairman 

 Arnold H. Smith, secretary 

 Committee reports: 

 Executive: C. W. Bedford, chairman. 

 Accelerator : J. B. Tuttle, chairman. 

 Physical testing: C. 0. North, chairman. 

 Discusion of "Methods of Research Testing" 

 by committee. 



Analytical Standardisation: S. Collier, 

 chairman. 



American conclusions regarding crude rubber: 

 (By title) : O. de Vries. 



Chemical reactions of sulfur terpenes with 

 rubber. I: John B. Tuttle. 



Studies in vulcanization: mechanism of the ac- 

 celeration of vulcanization of zinc ethyl xantho- 

 genate: H. A. Winkelmann and Harold Gray. 

 The gaseous, liquid and solid decomposition 

 products of zine ethyl xantliogenate are shown to 

 have no accelerating value. The activity of zinc 

 ethyl xanthogenate as an accelerator is due to the 

 unchanged molecule. 



Effect of certain tread pigments on tempera- 

 ture developed in pneumatic tires: D. F. Graver. 

 The paper is a short description of tread com- 

 pounds used, stress-strain curves of same, ■the- 

 oretical conductivity as calculated by WilUanis 

 formula, and the actual heating up of tire built 

 with such treads when run on the road, tempera- 

 tures being taken by means of thermo couple 

 inserted by the awl which was devised by tlie 

 researcli department of the New Jersey Zine 

 Company. 



Disubstituted guanidines: Winfield Scott. 

 Disubsubstituted guanidines function as accelera- 

 tors as amines and belong to the class of hydro- 

 sulfide accelerators only. Diphenylguanidine reacts 

 with hydrogen sulfide and carbon bisulfide to form 

 a trithiocarbouate, with aniline and carbon bisul- 

 fide to form a dithioearbamate and with carbo- 

 diphenylimide to form tetraphenylbiguanide. The 

 effect of small amounts of zine oxide and zinc 

 carbonate on tlie tensile strength of rubber cured 

 with disubstituted guanidines is q-uite marked. 

 Tlie relative curing powers of di-p-tolylguanidine, 

 di-o-tolylguanidine and diphenylguanidine are in 

 the order named, the first being the most efficient. 

 It requires 25 per cent, more diphenylguanidine 

 than di-o-tolylguanidine to produce the same ac- 

 celeration. 



Studies in hysteresis of rubber compounds: 

 W. W. VOGT. 



Thermal changes during vulcanization: Ira 

 Williams and D. J. Beaver. The measurement 

 of the temperature developed in the center of a 

 cylinder of rubber sulfur mixture which is im- 

 mersed in a constant temperature batli shows that 

 heat is liberated during the first stages of the 

 reaction. An absorption of heat is indicated 

 during the later stages. The extent of these 

 thermal changes has been estimated when stocks 

 of different sulfur and accelerator content were 



