130 CONJUGATED. 



M. Decaisne, and Mr. Jenncr regard as the true spores, but 

 which, Agardh declares, resolve themselves after a time into 

 zoospores, an opinion in which I concur, applying the term 

 sporangia to them. 



The tubes of communication do not appear to issue from 

 any determinate point of each cell, but from that which lies 

 in nearest contact with a neighbouring filament ; the filaments 

 appearing to exercise a mutual attraction on each other : thus 

 a number will be given off in succession to corresponding 

 ones of a filament near to it on one side, while another set from 

 the same filament will unite with those of another coming 

 near to it in some other part of its length. 



It is curious to remark that the cells in one part of the 

 same filament will part with their contents and remain 

 empty, while in another, they will be the recipients of the 

 contents of the cells of another filament. 



This remarkable mode of union of the filaments, almost 

 without parallel in the vegetable kingdom, was first noticed 

 by Mullcr in a species which he named Conferva jugalis. 

 Miiller, however, did not entertain the slightest suspicion that 

 it was in any way connected with reproduction. 



Since the time of the publication of Vaucher's " Histoire 

 des Confcrves d'Eau douce," in 1803, but little seems to have 

 been added to the information contained in that excellent 

 work in reference to this division of the Alga, in which the 

 phenomenon of union of the cells is shewn to belong to very 

 many species, which Vaucher for the most part has satisfac- 

 torily determined, notwithstanding the feeble power of the 

 instrument employed by him in their investigation. The 

 labours, however, which I have bestowed upon the fresh- 

 water Al(j(R have been rewarded with a few discoveries of 

 interest, one of which I shall now proceed to notice. 



This relates to the fact, that certain species of Conjugated;, 

 l)clonging principally to the genus Zygnema, occur, in which 

 there is no union of the different filaments similar to that al- 

 ready described ; the sporangia being formed in these by the 

 concentration of the matter of two cells in the same, and not 

 as in the preceding casern different, filaments. This interest- 

 ing fact was first announced by me in a paper on the Zyyne- 



