230 NATURAL SCIENCE [October 



in a subsequent note to this paper the authors state that they have 

 found a great number of ArchacocyatJiinae at Normanville in lime- 

 stone, which " appears to be conformable to strata which most resemble 

 those in which the radiolarian casts have been observed." Hence 

 they are inclined to believe that the Eadiolaria may be in Lower 

 Cambrian or passage beds rather than Pre-Cambrian. 



Freezing of Plants 



Messrs G-ustav Fischer, of Jena, have just issued, in book form 

 (73 pages 8vo), an account of some researches by Prof. Hans 

 Molisch on the freezing of plants. The author, by means of an 

 arrangement which he describes in the first chapter, has observed 

 under the microscope the changes which occur in freezing not only 

 in plant-cells and tissues, but also in colloidal substances, emulsions, 

 coloured liquids, and salt-solutions. For observation the microscope 

 is placed in a triple box. The outer case is of wood, then comes a 

 hollow-walled zinc chamber, inside which is fitted the instrument, 

 the tube projecting through the top. Sawdust is placed between 

 the outer wall and the zinc chamber, and the hollow walls of the 

 latter contain the freezing mixture. A wide zinc tube allows 

 light to pass from the outside to the reflector. Several figures are 

 given, showing the appearance of non-living substances as freezing. 

 In all cases particles of ice are formed by separation of the water, 

 while the gum, particles of latex or concentrated salt-solution 

 occupy the intervening spaces. Three figures (p. 17) of an amoeba, 

 alive, frozen, and thawed respectively, are of interest. In the 

 frozen state the organism forms a lump of ice intersected with a 

 highly complicated network, consisting of protoplasm very poor in 

 water, concentrated cell-sap and air-bubbles. When thawed there 

 is a much less sharply defined reticulum of dead protoplasm, the 

 lacunae in which are the spaces which in the frozen state were filled 

 with ice. Spirogyrci cells (p. 22, fig. 10) in freezing lose about half 

 their diameter by withdrawal of water, which then freezes on the 

 outside ; on thawing the cells swell to their original size, but proto- 

 plasm, chlorophyll band and nucleus form a disorganised central 

 axis between which and the walls is contained the water. 



After experimenting for five winters with hundreds of objects, the 

 author comes to the conclusion that, as a rule, it is immaterial to the 

 preservation of the life of the object whether thawing is rapid or 

 slow, and that death by freezing is the result of an excessive loss of 

 water, through ice formation, if the protoplasm by which its struc- 

 ture (" architektur ") is destroyed, and that all the facts of the case 

 can be easily and natui'ally explained from this point of view. 



