AKCHEB. ON TALMOGLCEA MACEOCOCCA (kUTZ.). 29 



not exactly see that the species of " Palmogloea" which fall under Cy- 

 lindrocystis rank themselves under the Desmidiaceae with the same 

 amount of prohability as regards the mode of growth alluded to. In 

 other words, I do not see that the same supposed evidence can he so 

 readily drawn from internal sources as in Mesotsenium of the addition 

 of two new half-cells between the old ones in vegetative growth. It 

 might be assumed, indeed, in Cylindrocystis Brebissonii, as cell-division 

 is preceded by a division of the central corpuscles belonging to each 

 half of the parent-cell, which now, therefore, contains four such, each 

 equal in size to each of the two former, and as those nearer the ends 

 seem to occupy the same relative position in respect of, and distance from, 

 the ends, as the original ones did at first, in fact, apparently precisely 

 the same situation, that the new space provided for the accommodation 

 of the two inner corpuscles is due to the addition at the centre of an 

 extension of the cell-wall, which, after division, forms the new half-cells. 

 But the central pale space is present throughout, and the division of the 

 corpuscles is preceded by their elongation, the whole in the direction of 

 the axis of the cell, as if this might be due to a gradual external exten- 

 sion all over of both corpuscles and external wall. Indeed, in C. crassa 

 (De Bary), which, as hereinbefore spoken of, occasionally presents its 

 young recently-divided cells elongating in a direction at right angles to 

 the longitudinal axis, of the mother- cell, there apparently takes place an 

 elongation equally at both ends of the nascent cells. Moreover, in this 

 genus the parent-cells seem to incorporate during conjugation, and do 

 not split as if at a suture, the zygospore finally free within the cavity 

 formed by the parent cells. But, again, the plants themselves seem to 

 have considerable affinity to the genus Penium (Breb.), but, as it seems 

 to me, as Spirotsenia, Mesotsenium, and Cylindrocystis, as I have above 

 endeavoured to point out, are distinguished from each other by their 

 internal structure, so I believe is Penium distinguished from those by 

 its internal structure. In Penium the granular contents form an axile 

 mass, sending out all round in some species, more or less irregularly 

 divided, or in other species quite uninterrupted plates to the cell- wall, 

 which appear outwardly as more or less interrupted, or irregular, or 

 tolerably uniform longitudinal bands, in end- "view radiate ; but in these 

 and other respects, as regards the species, characteristically disposed, and 

 of course often containing starch-granules, or " chlorophyll-vesicles." 

 This is briefly the character distinguishing this from the three other ge- 

 nera we have been considering. It is undoubtedly Desmidian. Although 

 Spirotsenia has always also been so considered, as already said, conjuga- 

 tion has not been seen in it. 



Such then is, so far as I can see, and as briefly as I can put it, the 

 state of the case as regards the position of the Palmogloean species. 

 "Whether they be regarded as Desmidians, or as connecting that family 

 with the Palmellaceae, or what place amongst the Algae near them they 

 may be eventually thought to hold, they appear to me, at least, very 

 well distinguished as genera and species. 



Reverting now to the description of our plant given above, I would 



