334 On the Formation of the Spore in a species of Vesiculifera. 



portunity of satisfying myself as to the real character of the pro- 

 cess, and I can give the following as the result, not only of my 

 own observations, but fortified by the opinion of Mr. Berkeley as 

 to their correctness, to whom I submitted specimens for exami- 

 nation. 



The species in question may possibly be the V. lacustris of 

 Mr. Hassall, with which species it would appear to agree in size, 

 but I cannot determine with any certainty from his figure and 

 description. The plant occurs in ponds on a common near Bristol, 

 and is of a pleasant pale apple-green colour. The cells are usually 

 from five to seven times as long as broad, and are lined with but 

 a small quantity of endochrome which is disposed in a reticulate 

 manner. Some of the cells, however, may be observed to be 

 slightly inflated, and to contain a larger amount of endochrome 

 than the rest : in each of these inflated cells a spore is subse- 

 quently formed, and in the following way : — The endochrome, 

 after attaining a certain degree of density from an increase in its 

 development, not from any derived from a contiguous cell, moves 

 towards one end of its cell ; it (the endochrome) shortly becomes 

 divided into two very unequal portions, the larger and terminal 

 one of which becomes converted into the spore, and the smaller 

 portion is found to be separated from this by a single septum. A 

 process has, in reahty, taken place analogous to the fissiparous 

 division of the cell of Zygnema ; two cells have been formed 

 within the original one, but in the Vesiculifera one of these new 

 cells is the spore. 



This is a fact of considerable physiological importance, and I 

 shall have more to say on this subject in a future communica- 

 tion. 



P.S. March 25, 1846. — Since writing the foregoing I have re- 

 ceived a letter from Mr. E. Jenner, who is well-acquainted with 

 the species intended by Mr. HassalFs descriptions, informing me 

 that the Vesiculifera mentioned above is the V. concatenata of 

 that gentleman^ s work. 



I have today examined very carefully specimens of Vesiculifera 

 aqualis, Hassall, and find that the process of the formation of the 

 spore is similar to what I have stated to take place in V, conca- 

 tenata. In the V. (Equalis, however, I have been able to trace 

 the mode of development of the two or three contiguous spores, 

 which are sometimes to be seen in the filaments of this species : 

 the first spore is formed in the way I have previously mentioned, 

 and arrives at considerable maturity before there is any appear- 

 ance of one, contiguous to it, being produced ; but it may then be 

 seen that the smaller portion of endochrome, which had been 

 separated just previously to the first spore being formed, and 



