108 SCIENCE PROGRESS. 



assumes that they are products of minute bodies called 

 tonoplasts, is of itself improbable, and is contrary to the 

 teaching of observations which may readily be made on the 

 constitution and behaviour of vacuoles in living protoplasm. 

 It has been shown by Butschli l that the contractile and 

 other vacuoles of Protozoa continually make their appear- 

 ance without owing their origin to the division of previously 

 existing vacuoles. It is not possible to go into details here, 

 but the reader will find a full discussion of this question in 

 Butschli's work (p. 230) as also a resume of the various 

 theories which have from time to time been put forward on 

 the subject of the granular theory of protoplasm. But even 

 if peculiar views on the nature of vacuoles be laid aside, 

 the gist of Wiesner's arguments is not materially weakened. 

 None of the structures which are observable in protoplasm 

 are observed to originate neogenetically : they are all, he 

 says, derived directly by division from pre-existing struc- 

 tures of similar character. In short, he fully accepts the 

 aphorism put forward somewhat earlier by Altmann : 

 " Omne granulum e granulo ". Wiesner does not definitely 

 say that the various particles observable in protoplasm are 

 to be severally identified with the ultimate vital units, his 

 plasomes. Some of them may be individual plasomes, but 

 the majority of them are, he thinks, aggregates of plasomes, 

 units of a hioher order which in turn are combined to form 

 the still higher unit the cell. Thus he presents a scheme 

 of organisation which, instead of taking the cell as the 

 lowest structural unit, goes several grades lower ; instead 

 of the old conception of 



organ — tissue — cell, 



he represents the scheme of organisation as being 



organ — tissue — cell — granules — plasomes. 



A detailed criticism of Wiesner's views would occupy a 



much larger space than I have at my disposal, and such a 



criticism is unnecessary, since all that need be said has 



1 O. Butschli, Investigations on Microscopic Foams and Protoplasm. 

 Authorised translation by E. A. Minchin. London : A. and C. Black, 

 1894. 



