PRINGSHEIM, 0\ CHRONIZOOSPORES OF HYDRODICTYON. 55 



liberty. This circumstance has even been supposed to fur- 

 nish a useful character by which zoospores may be distin- 

 guished from other reproductive bodies (Samen-Korper). 



But, besides those zoospores which germinate immediately, 

 as nearly all those known at the present day do, I have dis- 

 covered the existence of others whose destination is very 

 different. 



These particular zoospores, far from germinating the mo- 

 ment they become still, have the power of remaining nearly 

 in the same condition for a longer or shorter time, according 

 to external circumstances, or even of undergoing an absolute 

 suspension of development. 



This phenomenon recalls, by an . evident analogy, what is 

 known of the encysting of the Infusoria, to the most simple 

 forms of which zoospores bear such a strong external re- 

 semblance that it is difficult to distinguish them without 

 having followed out their development. 



The zoospores of which I am about to speak differ from the 

 ordinary zoospores belonging to the same species, not only in 

 the prolonged period of latent and inactive life w'hich suc- 

 ceeds their activity, but also in the nature of the phenomena 

 which mark the end of this period, and their entrance into 

 a new life. In all other respects they resemble ordinary zoo- 

 spores, they have the same form and the same structure, and as 

 to their morphological signification, they are also to be classed 

 with those reproductive bodies by whose agency the multipli- 

 cation of the plant to which they belong is effected without 

 the aid of sexes. Side by side, then, with the zoospores which 

 germinate immediately, there are others whose germination 

 may be normally suspended or deferred, and which I propose 

 to call Chronizoospores (Dauerschwaemner).^ 



The plant *in which I shall show the presence of this par- 

 ticular kind of zoospore is Hyclrodictyon utriculatum. 



This curious alga has been studied by so many naturalists, 

 and its history is so rich in interesting details, that as it will 

 be impossible for me to give them all here, I shall only refer 

 briefly to such as bear directly upon the subject of this 

 notice. 



After Vaucher, in the year 1800, discovered that young 

 Hydrodictyons were engendered in the cells of the adult 

 plant, and escaped thence completely formed, M. Trevi- 

 ranus satisfied himself that these new individuals owed 

 their origin to isolated graniiles, which, before they united 

 into a network, had the power of moving freely within the 

 mother-cell. However, he was not able to demonstrate this 

 [* Statospore (Hicks).'] 



