260 F. 0. EOWEE. 



chromatophores of conjugating cells of Spirogyra, and also in 

 other examples. 



The disappearance of chromatophores by resorption has been 

 seen in various examples, often in cells which are destined 

 exclusively for a definite function. This process of resorption 

 is accompanied, or rather preceded by a disappearance of the 

 pyrenoids also ; but the disappearance of a pyrenoid has never 

 been observed in active vegetative cells. This fact is strong 

 evidence that the pyrenoid is not a lifeless body included in 

 the chromatophore, but rather an actively living part of it ; the 

 attempt on the part of Meyer {' Bot. Zeit./ 1883, p. 493) to 

 show that the pyrenoids described by Schmitz are really crys- 

 talloids fails in a very essential point; since he admits (p. 494) 

 that he has never seen the pyrenoid disappear entirely in 

 specimens of Spirogyra, which he had starved. 



For further details, and especially on the bodies contained in 



chromatophores, readers must be referred to the original paper. 



In conclusion, a few general remarks upon the bearing of 



the remarkable discoveries above described may not be out of 



place. We have seen how three separate observers, working 



separately,^ and almost simultaneously, have arrived at very 



similar results ; it is rarely that such unanimity is attained, 



and we must regard the fact as establishing those main points 



in which their evidence agrees, upon an unusually firm basis. 



I refer especially to the conclusion that, as far as experience 



goes as yet, plastids are not formed free in the protoplasm, but 



are the products of division of pre-existing plastids. It must 



be allowed, however, that the proposition cannot be at present 



stated without the limitation given above. It still remains to 



be shown among vascular plants (1) how the plastids are 



transmitted, if indeed they are transmitted, from the parent 



plant to the oosphere ; and (2) what part they take in the 



process of fertilisation. Another point of great interest will 



be to ascertain whether the distribution of plastids in one form 



or another be coextensive with that of nuclei ; or in other 



^ Prof. Schmitz made at least the most important of his observations at 

 Naples, not at Bonn, 



