906 SUMMARY OF CURRENT RESEARCHES RELATING TO 



diatom-shells, &c. ; this is seen in Difflugia and its allies, and here a 

 portion of protoplasm is extended from the mouth of the shell, and 

 remains in connection with the mother until it has become nucleated 

 and got its investment. For this purpose the parent cell has pre- 

 viously collected the material, so that the daughter-cell rapidly 

 becomes shelled. 



BOTANY. 



A. GENERAL, including- Embryology and Histology 

 of the Phanerogamia. 



Chemical Difference between Dead and Living: Protoplasm.* — 

 What it is which constitutes life, whether it is produced or not by a 

 non-material principle, i.e. by a "force" akin to the natural forces, 

 heat and electricity, are questions which have been agitated, and to 

 answer which theories have been evolved ever since the Microscope 

 revealed to us the apparently extreme structural simplicity of the 

 physical basis of life. Dr. O. Loew and T. Bokorny's recognition 

 of a definite chemical difference between the characters of protoplasm 

 before and after death will be interesting to those who have felt the 

 said theories to be unsatisfactory, even if plausible. Dr. 0. Loew 

 elaborated last year a theory, according to which protoplasm consists 

 of an aggregation of aldehydes, the cai^ability of an intermolecular 

 motion of which was a necessary condition of life, the destruction of 

 this equilibrium resulting in death. To put this to the proof, the two 

 authors above mentioned have now endeavoured to find in living proto- 

 plasm the aldehydes demanded by this theory. Nitrate of silver, in a 

 solution of 1 : 100,000, that is, of a strength too slight to react visibly 

 with hydrochloric or hydrosulphuric acid, was used to test the 

 chemical properties of the protoplasm. Small quantities of the 

 filamentous Algae Spirogyra and Zygnema were placed in a litre of 

 this solution ; they soon assumed a brown colour, and in twelve 

 hours many of the cells were deeply stained black. A study of the 

 distribution of the reduced silver in the plant shows that the reduc- 

 tion process was most active at the septa between the cells and in the 

 chlorophyll-granules, and at plications in the cellulose walls. If the 

 Algae are first killed they show no trace of the reaction. If they are 

 kept for five minutes at a temperature of 35° C. the reaction is toler- 

 ably active, but at 50° the protoplasm becomes wholly inactive in this 

 respect. This agrees with Max Schultze and Kiihne's observation 

 that various low organisms and cells are killed by a heat of between 

 45° and 48° C, although it must be remembered that Max Schultze 

 found Algfe living at 53° C, and Ehrenberg at 81° to 85° C, and that 

 Naegeli found that Bacillus suhtilis survived boiling for eleven hours. 

 Besides heat, ether vapour, applied for an hour to filaments dried in 

 blotting-paper, kills them ; also an immersion of one hour in either 

 sulphate of copper, sulphuric acid, or caustic soda. In opposition to 



* Pfluger's Archiv, xxv. p. 150. Of. Naturforscher, xiv. (1881) pp. 290-3. 



