368 



SCIENCE. 



[N. S. Vol. XII. No. 297. 



tions of differentiation within the cell plasm. 

 In many cells there appears also to be a 

 difference in the character of the cell plasm 

 which immediately surrounds the nucleus 

 and that which lies at and near the peri- 

 phery of the cell. The peripheral part 

 (ektoplasma) is more compact and gives a 

 defijiite outUne to the cell, although not 

 necessai-ily differentiating into a cell mem- 

 brane. The inner part (endoplasma) is 

 softer, and is distinguished by a more dis- 

 tinct granular appearance, and by contain- 

 ing the products specially formed in each 

 particular kind of cell during the nutritive 

 process. 



By the researches of numerous investi- 

 gators on the internal organization of cells 

 In plants and animal, a large body of evi- 

 dence has now been accumulated, which 

 shows that both the nucleus and the cell 

 plasm consist of something more than a 

 homogeneous, more or less viscid, slimy 

 material. Recognizable objects in the form 

 of granules, threads, or fibers can be dis- 

 tinguished in each. The cell plasm and the 

 nucleus respectively are therefore not of the 

 same constitution throughout, but possess 

 polymorphic characters, the study of which 

 in health and the changes produced by dis- 

 ease will for many years to come form im- 

 portant matters for investigation. 



William Turner. 

 {To be concluded.) 



EXPEBBIENTS OF .T. J. TH03IS0N ON TEE 

 STRUCTURE OF TSE ATOM. 



E.ECENT ideas as to the stability of the 

 chemical molecule have been much modi- 

 fied by the evidence that it is readily dis- 

 sociated when a substance is dissolved in 

 water. 



The researches now being carried on by 

 J. J. Thomson and his assistants on the 

 electrical conduction of gases seem to re- 

 quire an even more radical and sweeping 



change in our conception of the structure 

 of the atom itself. 



Ordinary gases are perfect non-conductors 

 of electricity of low electromotive force. 

 Electricity may, however, pass through 

 them, more or less readily, under certain 

 conditions, viz : 



1. When the electromotive force is suffi- 

 cient to produce a spark. 



2. When the pressure of the gas is much 

 reduced and a sufficient electromotive force 

 is applied ; as in a ' vacuum tube.' 



3. When the gas is heated very hot, or 

 has been recently in violent chemical ac- 

 tivity, as in the region above a flame. 



4. When the negative electrode is illu- 

 minated by ultra-violet light. 



5. When the gas has been very recently 

 exposed to Rontgen rays or to the similar 

 rays proceeding from uranium, radium, 

 etc. 



Thomson's investigations on the conduc- 

 tion by sparks through gases at ordinary 

 pressures, indicated that electrolysis took 

 place somewhat as in solutions, and that 

 the amount of decomposition was, in several 

 cases, essentially the same as in the de- 

 composition of solutions. In the case of 

 hot gases and the gases in a vacuum tube, 

 also there was evidence that the conduction 

 was by means of ' ions' or portions of 

 broken-down molecules which acted as car- 

 riers for the current. 



When an electric current passes through 

 a solution, it is a fundamental law that a 

 univalent atom of any substance carries 

 precisely the same charge as a univalent 

 atom of any other substance, while a biva- 

 lent atom carries just twice this charge. 

 The exact charge carried by one atom can- 

 not be known until we know the exact 

 weight of the atom ; but the charge carried 

 by 1 gramme of atoms (e/m) is about 10,000 

 units in the case of hydrogen. For any 

 other univalent substance, the weight re- 

 quired to carry this charge is greater in 



