DUBLIN UNIVEESITY ZOOLOGICAL AND BOTANICAL ASSOCIATION. 243 
this phenomenon of moving granules as displayedhy my new form. The 
foregoing are the principal arguments for the animal nature of these 
organisms, which clearly do not hold good. On the other hand, the 
arguments in favour of their vegetable nature are more numerous and 
convincing. The cell-wall composed of cellulose, the presence of starch, 
the multiplication of the cells by transverse division in a manner ana¬ 
logous to other Algse, the reproduction by conjugation and formation of 
sporangia similar to other Confervoids, their herbaceous green colour 
owing to the presence of chlorophyll, the rotation of their cell-contents, 
&c., all combine in proving their vegetable nature. Nor are special 
points of affinity wanting with various neighbouring groups of Algae, 
irrespective of the Diatomacese. Eor instance, they approach the Pal- 
mellaceous Algse by their gelatinous nature and likeness of form in some 
species of Penium ; to the TTlvaceous Algse they approach through such 
as Scenedesmus obtusus, connected with Merismopsedia; Spirotaenia con¬ 
siderably resembles a joint of Spirogyra; while a form to be brought to 
notice presently and its congeners point, I apprehend, to the Zygne- 
macese. 
The Desmidiacese occur in shallowish, undisturbed ponds in open 
exposed situations, such as little pools on boggy moors and commons, 
permanent ponds in old quarries, &c. A few are met with in gently 
flowing water. They are either mixed imperceptibly with the mud, or 
disposed in a green stratum on the bottom, or projecting in little tufts, 
or floating in little gelatinous masses on the surface, or forming a cloud¬ 
like mass investing the submerged leaves of aquatic plants, or sparingly 
scattered amongst the masses of filamentous Confervoids. Several species 
are quite common, but as a group they are more local in their distribu¬ 
tion, than, as a group, are the Diatomacese, the commoner species of 
which occur almost universally. 
Having thus tried, as briefly as I could, to communicate an epito¬ 
mized account of the nature and appearance, and of the distinctive cha¬ 
racters of this group of Confervoid Algse, and because an explanation 
seems to be due for obtruding so much that is not new, I would beg 
again to remark that I have undertaken it for the use only of those of 
our members who may be unacquainted with the facts and details brought 
forward. I will now pass on to describe my new forms, being that por¬ 
tion of this communication to which any interest will be likely to attach 
on the part of those who are experienced. 
I have now to bring to notice an Alga which, to the naked eye in 
the mass, and perhaps at first sight under the microscope, does not at 
once strike the observer as belonging to the Desmidiacese. The organism 
in question forms rather dense masses of filaments, sometimes an inch or 
two or more in length, attached to aquatic plants, and, in the mass, is of 
a bright and beautiful green, and of an elegant appearance, like “ floss 
silk” in the water. When placed under the microscope, the filaments 
are seen to be composed of very greatly elongated joints, of moderate 
diameter, with truncate ends, and possibly might, at a hasty glance, be 
taken for a Mesocarpus, or some allied form. Probably the first circum- 
