and on a new Species of Protococcus. 429 



General Observations. 



Thus we have seen (1) that the development of Sorastrum 

 spinulosum commences by a division of the contents of the 

 sporangium into sixteen portions or family groups of eight 

 (sixteen, or thirty-two?) individuals each; (2) that, after elimi- 

 nation, these groups increase in size, but not in number of 

 individuals, so far as my observation extends ; (3) that certain 

 individuals produce one or more family groups of eight, six- 

 teen, or thirty-two individuals each, in cells respectively pro- 

 vided by the parent, which are deciduous (that is, subse- 

 quently soon disappear) ; (4) that those individuals of the 

 parent group which do not produce new families retain their 

 gonimic contents, increase in size, become globular, and lose 

 their spines by atrophy ; (5) that a spherical or slightly ellip- 

 tical sporangium, about twice the diameter of the largest in- 

 dividual of a group of Sorastrum, makes its appearance, pre- 

 senting a deep dark sea-green colour, precisely like that of 

 Sorastrum, composed of a tough, transparent coat filled with 

 the usual contents of a sporangium, and suiTOunded by a thick, 

 soft, transparent, gelatinous envelope. 



It may noAV be asked, upon what grounds I assume that 

 the first development of Sorastrum witnessed was that of the 

 sporangium. To which it may be replied, that it presented 

 features which none of the other developmental forms pos- 

 sessed, viz. a large spherical cell containing sixteen family 

 groups, while no other but the " baby " group was enclosed 

 in a proper cell, and the cell of this group was deciduous. 

 Again, no other developmental form of the kind presented 

 itself after the 18th July ; but, on the contrary, a great num- 

 ber of groups of eight, sixteen, and thirty-two individuals 

 made their appearance, followed, after the 10th of September, 

 by a still greater number of baby groups which they produced. 

 Hence there was a direct sequence in the appearance of the 

 sporangium, the free parent groups, and the baby groups re- 

 spectively. 



A more perplexing question, however, is the signification 

 of the increase of size, rounded form, and atrophy of tlie spines 

 in those individuals of the group which retained their gonimic 

 contents but did not produce baby groups. This I cannot 

 answer further than that these may pass into winter forms, or, 

 being impregnated, resolve themselves into sporangia. 



Nor has the mode of impregnation been witnessed. But 

 here, I think, it may be fairly assumed, from what has been 

 seen in the impregnation of a unicellular Alga (Annals, I. c), 

 that, on the evolution of the gonimic contents (in September) 



