188 ARCHER, ON SPIROTAENIA. 
a little ribbon—those granules, which or dinarily are more or 
less scattered, and which thus tend in a certain degree to 
obscure the actual characteristic spiral arrangement of the 
endochrome, seem then to be absent—then the nucleus and 
its nucleolus come out to view in perfection. Indeed, it is 
hardly possible to see a more elegant object than a favorable 
specimen of this handsome species, which shows the nucleus 
in side view and the light so shed from the condenser as to 
fully illuminate the whole cavity and clearly to display its 
characteristic and beautiful arrangement. 
I have not yet been able to detect a nucleus in any other 
species of Spiroteenia; perhaps, as in S. condensata, it re- 
quires favorable circumstances to reveal it. I am, however, 
the more desirous to draw attention to it as it exists in the 
species under consideration, inasmuch as it forms a seemingly 
noteworthy exception to other Desmidiacee in this regard. 
In all other species in which the nucleus can be seen it is 
orbicular and central; nor does de Bary, in his work on the 
Conjugate, draw attention to the peculiarity in this species 
which [ have pointed out—nay, his figure* leads to the idea 
that he regarded the nucleus as central ; but this may, indeed, 
arise from his having seen and drawn it either from above or 
below, and not from the side, which, as I have shown, would 
be deceptive. 
Another reason which causes me to think it advisable that 
attention should be drawn to the form and position of the 
nucleus in this species is the possibility that observers might 
imagine, upon casually viewing an example, that it perhaps 
represented nothing but a detached joint of a Spirogyra. 
Such a mistake, indeed, I could hardly imagine possible 
when sufficiently closely examined ; but even if it de possible, 
I think, due regard being had to the circumstance that the 
nucleus in Spirotenia condensata is semiorbicular and parietal, 
whilst in Spirogyra it is equally compressed and central, 
ought at once to preclude the chance of any confusion. 
To pass on to the conjugated state. 
When I first examined the gathering, in which this species 
occurred more than usually copiously, my attention was at- 
tracted by the number of cells lying side by side over the 
field of view in parallel pairs. Under such circumstances it 
is always well not to lose sight of the specimens of whatever 
species may be so encountered, as it betokens impending con- 
jugation ; accordingly I placed these aside for further ob- 
servation. Nor was there any disappointment in this case. 
The following is the process: 
* Op. cit., ft. v, fig. 12. 
