INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 609 



ence of an isolated individual from the moment of its birth to its com- 

 l)lete transformation and maturity. 



In a subsequent paper * Dr. Lanzi replies to M. Petit's criticisms 

 and reaffirms his belief in the correctness of his previous observations. 



Systematic Position of the Volvocinese.t — M. E. Maupas criticizes 

 in a recent number of the ' Coinptes Eendus ' the view put forward 

 by Stein (in his ' Flagellate Infusoria '), that the Volvocineae are 

 Infusoria, thus returning to Ehrenberg's opinion and reopening the 

 old discussions which after the researches of Cohn might be supposed 

 to have been closed for ever. 



According to Stein the true criterion which distinguishes a 

 Protozoon from a Protophyte is the presence of vibratile flagella, con- 

 tractile vacuoles, and a nucleus combined in one organism. The 

 Protozoa alone combine these three, and it is upon this view that 

 he excludes the Volvocinefe from the vegetable kingdom, and places 

 them among the Flagellate Infusoria. 



M. Maupas considers Stein's criteria to be without value, the three 

 characteristics being found in algfc, whose vegetable nature Stein 

 would not venture to dispute. 



Everyone knows that all zoospores are provided with vihratile 

 cilia. 



As to the contractile vacuole it is astonishing that such an exact 

 and generally well-informed observer as Stein should still deny the 

 existence of this organ in the vegetable kingdom. It has been seen 

 by Leitgeb, De Bary, Fresenius, Strasburger, Dodel-Port, and Cien- 

 kowski, in the zoospores of the Saproleguieae, Myxomycetes, Ulothrix, 

 &c., and the writer himself has observed it in Microspora floccosa and 

 Stigeoclonium tenue, and is satisfied that it would be found in many 

 other zoospores if the research was made with sufficiently high 

 powers and in good conditions of observation ; at any rate the 

 numerous facts already established are sufficient to disprove Stein's 

 assertion. 



"With regard to the nucleus, Stein in denying its existence in the 

 zoospores of algae is no doubt in accord with most authorities. All 

 observers who since Thuret have studied these organisms have failed 

 to discover a nucleus, and Strasburger very recently J allows that the 

 nucleus of the zoospores of Ulothrix does n(,t exist during its free life 

 and is reconstituted at the moment of germination. M. Maupas, 

 however, by using methods of observation which he has long employed 

 for the study of the nucleus and nucleolus of the Infusoria, has 

 succeeded in discovering a very clearly defined nucleus in the zoospores 

 of Microspora floccosa, and of an CEdogonium. 



He places a small drop charged with zoospores of Microspora on a 

 piece of glass, covering it with the cover-glass and sucking out water 

 so that the zoospores should be somewhat compressed and rendered 

 nearly immovable ; he then cements with paraffin two of the 

 opposite margins of the cover-glass and draws under it a drop of 



* ' Brebissonia,' i. (1879) p. 129. 



t 'Coinptes Rcudub,' Ixxxviii. (1879) p. 1274. 



X ' Bot. Zeit.,' April 25, 1879, p. 274. 



