202 DR. COHN, ON THE DEVELOPMENT OF 



these bodies were animal existences, is perhaps indubitable, 

 from their phosphorescence ; but in what connexion they 

 stand with respect to the Noctilucce, associated with which 

 they occurred in large number, cannot at present be deter- 

 mined." 



Untersuchungen ueber die Entwicklungs-geschichte der 

 MiKROsKOPiscHEN Algen wid PiLZE. Von Dr. F. CoHN. 

 (Researches on the Development of the Microscopic Algae 

 and Fungi, By Dr. F. Cohn ; pp. 153 ; 6 Plates. Bonn, 



1854. 



The importance of the study of unicellular organisms, as 

 leading in the most ready and complete way to a knowledge 

 of the " cell," the foundation of all scientific acquaintance 

 with the real nature of plant life is so obvious, as to have 

 attracted a great number of followers. 



The fresh-water Algae, especially, afford abundant and 

 readily attainable materials for this study, and have, conse- 

 quently, formed the subjects of numerous writings. Amongst 

 those who have distinguished themselves in this field, the 

 name of Dr. Cohn will ever be held in deserved honour. 

 He has, for many years, as he says, devoted himself to this 

 study ; and, especially, to the remarkable propagation of 

 most of these Algae by means of motile cells (swarm-spores) ; 

 a mode of reproduction which has been observed in most of 

 the fresh-water species. The same phenomenon has also at- 

 tracted the attention of numerous other observers, and been the 

 subject of several memoirs. Among the more important of 

 these, exclusive of Dr. Cohn's, may be noticed the observations 

 respecting it contained in Dr. Braun's remarkable work on 

 ' Rejuvenescence in Nature,' of which a translation by Mr. 

 Henfrey has lately been published by the Ray Society ; and 

 the ' Recherches sur les Zoospores des Algues et les Anthe- 

 ridies des Cryptogames ' of M. Thuret. The appearance of 

 these independent memoirs appears to have turned Dr. Cohn 

 from his original intention of publishing a special treatise on 

 the ' Swarm-cells of the Algae,' and to have decided him 

 merely to give separate essays on those points appearing to 

 him to demand further attention ; his former monograph on 

 the ' Development of Chlamydococcus {Protococcus) pluvialis,' 

 of which an abstract has also been published by the Ray 

 Society with figures ; and his Memoir in Siebold and 

 KoUiker's Zeitschrjft f. wiss. Zool. ' On a new genus from the 

 family of the Volvocina,' of which a translation has appeared 

 in the 'Annals of Nat. History,' 2nd series, Vol. x., p. 321, 



