ARCHER, ON PALMOGL@A MACROCOCCA. 127 
cell, the older halves of each remaining unchanged. But I 
imagine the probability of a new half to the chlorophyll-plate 
being formed in continuation of an old one is strengthened by 
the fact that in dividing cells, when discernible, the corpuscle 
therein imbedded is found near the end towards the septum, 
and in fully grown cells at the middle. I therefore suppose 
it must be inferred that this change of position of the im- 
bedded corpuscle is not due to any inherent movement of its 
own, but to an elongation of plate and cell at the end nearest 
to which it at first lies, or that at which division has only 
recently taken place. A similar argument I before applied as 
some proof of the Desmidian nature of my Leptocystinema 
Kinahani.* Again, I have stated that in our present plant 
(figs. 9 to 14), in the act of conjugation, a shedding of the 
parent cell-wall takes place, accompanied by a splitting, as it 
were, through a suture, indicating, as in the Desmidiacee, 
the point of union of the half-cells. It may be worth noting, 
too, that in Mesotenium chlamydosporum the free inner spore, 
finally formed within the zygospore, seems to find a parallel 
in the similar occurrence in Tetmemorus levis. All these 
characters point strongly to the Desmidiacee. 
But on the other hand, Mesotenium Braunii and M. vio- 
lascens (De Bary) seem to conjugate by complete participation 
of the parent-cell-membranes in the act; cases, too, in the 
present plant are not rare in which the parent-membrane 
cannot be detected, but it must, in such cases, have become 
either lost or dissolved. Al. Braun + seems to consider that 
the genus Palmoglea (Kiitz.) is more Palmellacean than 
Desmidian, but thinks that the greatest distinction between 
Cylindrocystis and Penium is the participation in the former 
of the outer cell-membrane in the act of conjugation. But 
our plant presents an example of a “ Palmogloea” in which 
the cell-membrane does not co-operate in the conjugative 
act. 
But, except that they are Conjugatz, exhibiting, according 
to De Bary’s researches, the character, dwelt on by him, of 
capability of self-division in all the daughter-cells originating 
from the zygospore, I do not exactly see that the species of 
«“ Palmogleea” which fall under Cylindrocystis rank them- 
selves under the Desmidiacez with the same amount of pro- 
bability as regards the mode of growth alluded to. In other 
words, I do not see that the same supposed evidence can be 
so readily drawn from internal sources as in Mesotenium of 
the addition of two new half-cells between the old ones in 
* © Natural History Review,’ O. §., vol. v, p. 243. 
+ Op. cit. (English translation), p. 135. 
