The Microscope. 347 



thousandth part of a millimetre and has already been adopted as a 

 standard of microscopical measurements under this signification by 

 numerous learned associations, among others we may remark, by the 

 American Society of Microscopists. From the Journal of the Royal 

 Microscopical Society for June (No. 64, p. 502) we are glad to note 

 that this article of Prof. Ruecker has been brought before the Coun- 

 cil of the Society and that the latter adopted a resolution to the 

 eflPect that the word micron (symbol f' ) should henceforth be used 

 in the Journal and in the official proceedings of the Society in the 

 place of micro-millimetre and to signify the microscopical unit of 

 one one-thousandths of a millimetre. — St. Louis Med. and Surg. 

 Journal. 



Vacuoles. — F. Went has, in the last part of Pringshem's 

 Jahrbiicher fur wissenschaftliche Botanik (vol. xix, pp. 295-356) 

 an exceedingly important paper on vacuoles. His conclusions, in 

 his own words, are as follows: "With the exception of the doubtful 

 spermatozoids, Cyanophyceae and Bacteria, all living cells contain 

 vacuoles, which are surrounded by a special living wall, which bears 

 the name of ' tonoplast.' In all young cells division and coales- 

 cence of vacuoles takes place. All normal vacuoles of a plant arise 

 through continual division from those of the oosphere. The tono- 

 plasts, considered as organs of the protoplasm, are of equivalent 

 origin with the nuclei and chronatophores. Since the vacuoles, even 

 in the youngest cells, are continually changing their. shape, proto- 

 plasmic movements must take place in them, and does not begin, as 

 Hofmeister thought, only after the meristematic state is past. Nor- 

 mal vacuoles never arise from the protoplasm. Pathological vacuoles 

 are formed by the disorganization of the nuclei and chromatophores. 

 The paper concludes with a summary of the present knowledge in 

 regard to the vacuoles." — Botanic Gazette. 



Variety in Form of Unicellular Alg^. — There is great 

 variety of form among the algse of fresh water, even among the 

 unicellular species. It might be thought that these species, where 

 the whole plant is composed of but a single eel , would present little 

 variety, especially when it is considered that such simple cells com- 

 monly float loosely in the water, and in situations enabling the sup- 

 posed normal spheroidal, cell-form to develop itself, free from 

 the influences of crowding or lateral stimuli. But not so simple is 

 the plan of nature, and a great range of shape exists among the sin- 



