258 ARCHER, ON A NEW SPECIES OF ANKISTRODESMUS, 



nules. It is true that Mr. Berkeley alludes to a circulation 

 of fluid contents in his Closterium Grifflthii (seen only under 

 a power ranging from 1000 to 1500 diameters); but this 

 circumstance is of no generic or specific importance. It is 

 commoii, indeed, in Dcsmidiacese. Again, in Closterium the 

 self-division is transverse, taking place at the middle of the 

 frond ; and, when completed, a new segment is merely a 

 rounded or somcAvhat triangular protuberance, and the frond, 

 consequently unequal (figs. 61 and 62 aiFord an example), 

 presently the new, short, rounded segment elongates into a 

 complete counterpart of the older segment, assuming what- 

 ever may be the mature characteristic specific form. In 

 Ankistrodesmus the self- division commences in a slightly 

 oblique manner, presently rendered more and more oblique 

 by the younger portions growing alongside one another 

 longitudinally, the process being again and again repeated, 

 until an aggregated fasciculus of cells, greater or less in 

 number, is produced. Now, the aggregated fasciculated cha- 

 racter of the cells in this genus has been, I apprehend, looked 

 upon as one of primary importance. I imagine it is only of 

 secondary, and in its place as primary, I should think, the 

 obliquely dividing, slender, attenuated cells should come, and 

 the circumstance of those cells being aggregated into fasciculi 

 (in^. falcatus, forming dense, fagot-like bundles) be regarded 

 rather as an accidental or secondary, but very far from un- 

 important, character. Free cells are frequently met with of 

 even A. falcatus, in which, on the other hand, the fagot-like 

 bundles are often very large, many cells (thirty-two at most. 

 Nag.) being combined together. It is only the most minute 

 species of Closterium that are comparable in dimensions with 

 any Ankistrodesmus. 



Now, my plant has not a transverse band at the middle 

 (in recent living specimens), but only a rounded, clear spot at 

 one side of the cell ; it has no clear space near or at the end 

 containing moving granules ; its self-division is oblique, and 

 the cells frequently remain combined in twos or fours ; there- 

 fore, I believe it is an Ankistrodesmus. It is true that, 

 unlike A. falcatus, the aggregated families do not form fagot- 

 like bundles, a character given as generic ; * but in that 

 species solitary cells, as well as small families of two or four 

 cells, are frequent, the larger number eventually arising fi'om 

 the self-division of a smaller. I have not been able to follow 

 out Niigeli^s observations as to the mode of growth in 

 A. falcatus, but in a plant which I refer to Ankistrodesmus 



* Ralfs, * British Desmiiiic?e/ p. 179 ; Kiitzing, ' Species Algaruui,' 

 p. 195 (Raphidium). 



