272 M. N. Pringslieim on the Pairing of Zoospores. 



As regards the systematic position and significance of the 

 species here introduced, it wonld seem, in the modification of 

 its denticles, to indicate a slightly closer relationship to the 

 ordinary- forms of the Annelida than the other representatives 

 of the genus, stylate setfe set in elevated prominences being 

 of such general occurrence throughout the Errantia and 

 Tubicola. 



XXIX. — On the Pairing of Zoospores, the Moi-phohgically 

 Fundamental form of Rejrrodiiction in the Vegetable Kingdom. 

 By X. Peixgsheim*. 



The author states that he has previously shown, from obser- 

 vations on some genera of the Zoosj)orece, that those reproduc- 

 tive cells which had been considered resting-spores are the 

 female reproductive organs. The male organs in some genera 

 have the form of small bodies more or less differing from the 

 zoospores ; in other genera they are so like the zoospores that 

 they appear to be only smaller forms of the latter. 



The views thence derived with regard to the multiplication 

 and reproduction of these plants might be assimaed to be ap- 

 plicable to all those Zoosporea' in which two forms of zoospores 

 are knowni, and in which the existence of resting-spores is 

 known or suspected. 



But in most genera of Algaj in which zoospores exist, 

 resting-spores have not yet been discovered ; and in those ge- 

 nera in which two forms of zoospores are known, it has been 

 assumed that both kinds are of the same nature, and that they 

 germinate without any sexual act. The author has shown 

 that in some genera which have two kinds of zoospores and 

 no resting-spores, the small zoospores, passing into a state of 

 immobility, become themselves resting-spores, and that these 

 resting-spores, produced by the so-called microgonidia, repro- 

 duce the mother plant. 



These different ^4ews must admit of being reconciled, 

 unless it be assumed that essential differences in the mode of 

 increase and reproduction exist in such nearly allied plants. 

 If it be not assumed that all the plants without resting-spores 

 are asexual, it must follow either that their resting-spores 

 remain to be discovered (which is improbable), or that in the 

 Zoosporece, and in their already known organs, the sexual act 

 takes place in a special manner not yet discriminated. The 



* From the ' Monatsbeiicht ' of the Royal Academy of Sciences of 

 Berlin, Oct. 1869. 



