109 



however, is not increased on the assumption of the stellate form by 

 the sporangium, it being no larger, nor in fact quite so large, as in 

 its earlier stage : in Zygnema varians, on the contrary, no inflation 

 occurs at the first formation of the sporangium ; but when it becomes 

 stellate in character, the original cell in which it was formed is in- 

 flated in an excessive degree, so as to cause no pressure on the long 

 projecting spines, and the cell assumes a form nearly globular. (PI. 

 XXII. fig. 2, 6 6). 



I consider this an important fact, as tending to prove the conti- 

 nued vitality of the original cell, even at this stage of the process. 



I much regret that I was unable, from various causes, to make any 

 observations during the second fortnight, consequently did not see 

 the mode of operation during the change to the stellate from the ve- 

 sicular state ; it is therefore scarcely prudent to hazard any conjec- 

 ture as to how such change is effected : I am, however, induced to 

 do so, in the hope that if an opportunity should occur to any other 

 observer, he will note particularly the process at the corresponding 

 period. 



From various appearances, not easy to describe, I imagine then 

 that the vesicles cohere and become condensed, and that the spines 

 proceed from the points of contact between the vesicles, consequently 

 that the number of spines is dependent upon the number of vesicles. 

 My observations on this species were brought to a sudden termina- 

 tion, by the bottle containing the specimen having been blown down 

 from a window-ledge, and the contents entirely lost. 



In another of the filamentous Alga — Lyngbya floccosa — I have 

 noticed a similar peculiarity ; I mean the ultimate production of a 

 sporangium with spines : but in this genus the spines are compara- 

 tively very short, and, what is very remarkable, arranged in a regular 

 helix upon the sporangium, which is ellipsoidal in form, the longer 

 axis forming the centre, about which the helix is coiled. (Plate 

 XXII., fig. 4). 



In a species of Vesiculifera, I have also noticed a tendency to a 

 spinous character in the sporangia; but when the observation was 

 made, the spines were so little developed as to be merely tubercles, 

 with the exception of one individual, in which they were excessively 

 delicate and hair-like. 



For the accompanying drawings, illustrative of the various appear- 

 ances I have been endeavouring to describe, both in this and in the 

 preceding paper, I am indebted to the kindness of Mr. I. R. C apron, 



TRANS. MIC. SOC. VOL. III. 2 



