and on a neio Species of Protococcus. 433 



pair, if present, was probably concealed behind its compa- 

 nion. 



This group was found among the portions of jelly of Ophry- 

 dium versatile &c. which had been placed in the second gum- 

 bottle mentioned, together with another group consisting of 

 four individuals. Indeed, as I have before stated, the second 

 gum-bottle now furnishes the finest groups of Sorastrum, both 

 collectively and individually, the former being, for the most 

 part, 13-6000ths inch in diameter, and the individual cell up- 

 wards of 5-6000ths inch broad. If the individuals of a group 

 have become unusually large and rounded (that is, 6-6000ths 

 inch in diameter), very slight pressure seems to separate them, 

 when they leave their stems behind and present such an even 

 round outline, in lieu of the cuneate extremity, that no one 

 would suppose there had ever been a point of attachment 

 there, although the spines still remain the same ; and this, 

 perhaps, may account for the absence of the stem in Nageli's 

 and Rabenhorst's figures respectively. The reverse is the 

 case in the earlier part of their career, where the group may 

 be torn to pieces, but the stems remain almost inseparably 

 attached to the individuals. 



I have now seen, at one time or another, individuals singly, 

 and in groups of two, four, eight, sixteen, thirty-two, and, 

 I think, sixty-four, which, with the enlargement of the single 

 individual of the group of eight mentioned, and its four pairs 

 of spines, &c., leads to the following inferences : — 



That Sorastrum may increase by binary division like other 

 unicellular Algse of the kind ; that this may take place in a 

 single individual isolated from the main group (which might 

 thus originate a new group), or in a single individual while 

 attached to the main group, or in all the individuals of a group 

 synchronously ; that the enlarged and rounded state of the 

 individual, and not the more or less bilobate form, indicates the 

 preparatory stage to binary division ; that, as a single indivi- 

 dual of a group may precede the rest in binary division, so the 

 groups may not always be a multiple of 2, although generally 

 so, nor have 2 for a common multiplier (that is, that one indi- 

 vidual only of a group of eight, dividing, would give nine, &c.) ; 

 that, contrary to what has been before inferred, the groups 

 need not always contain the same number of individuals as 

 when first eliminated from the sporangium, but may be in- 

 creased in this respect by binary division, after elimination ; 

 that the enlargement and sphericity of the individual therefore 

 may not lead to the formation of the sporangium, whatever 

 the atrophy of the spines may indicate, while, on the other 

 hand, the contents of the individual may be liberated from 



Ann. <Sc Mag. N. Hist. Ser.4. VoI'iy. 31 



