132 CONJUGATEiE. 



jugatmg species. If two kinds of reproductive matter exist, 

 as most suppose, they must both be contained in the same fila- 

 ment in these species ; but even this view cannot be received 

 when it is known that certain species of the family Conjugates 

 occur in which there is not even a union of the matter of two 

 cells, but in which the sporangia are formed separately within 

 each ; as in Mesocarpus notabilis and Zygnema mirahile. 



It would thus appear that no argument can be deduced 

 from the conjunction of the cells in the same or diiferent fila- 

 ments and the commingling of their contents in favour either 

 of the animahty or sexuality of the Conjugatece^ and that the 

 phenomenon, remarkable as it is, is subservient to some se- 

 condary purpose in the economy of these productions. 



The species of this group of Confervce may be found occa- 

 sionally in a state of conjugation during the entire of the 

 spring, summer, and autumnal months ; they are chiefly met 

 "with, however, in this state in the spring. It is usually some 

 days after this union of the cells has been established, that the 

 slow emanation of the matter of one cell occurs, this trans- 

 ference being occasioned apparently by the mutual attraction 

 exercised by the contents of each cell on that of the one to 

 which it is joined ; this attraction, in correspondence with the 

 law of gravitation, being predominant in that cell which con- 

 tains the greatest bulk of matter ; and thus, I think, we may 

 account for the contents of a number of cells of one filament 

 passing to those of another set of cells of another filament, 

 the matter in them being more considerable in quantity. 



Very soon after the contents of the cells have united, they 

 are seen to dispose themselves into a regular form, and in the 

 course of three or four days the sporangia are perfected, each 

 being invested with its two or three membranes. 



For some time, not unfrequently extending to weeks after 

 the cells have conjoined, and the sporangia have become or- 

 ganized, the species does not appear to undergo any further 

 change : at length, however, the tubes of communication 

 separate, the cells become disjointed, indicating the death of 

 the plant, respii'ation ceases, and the disunited fragments fall 

 to the bottom of the water, the sporangia being set free on the 

 entii-e disorganization of the plant or the zoospores bursting 



