Tue Microscope. 105 
PROTEROSPONGIA PEDICELLATA. 
DR. ALFRED C. STOKES. 
he the Journal of the Royal Microscopical Society for August, 
1884, Mr. Frederick Oxley describes a new member of Pro- 
terospongia, a genus of social collar-bearing monads, the chief 
peculiarity of the species being the posteriorly developed pedi- 
cle, on account of which he named the creature Proterospongia 
pedicellata. The Choano-flagellata, or collar monads, have as 
- yet attracted but little attention in this country, although few 
among the microscopic animals of the water are more graceful 
or beautiful. Their excessive minuteness, however, and the 
consequently high amplification needed for their study or even 
for their ordinal recognition, are not in their favor, although 
when once positively observed, the characteristic coliar encirel- 
ing the base of the flagellum can be demonstrated with a low 
power objective. One of Tolles’ superb ;4,ths is usually an effi- 
cient aid in seeking them, well defining the flagellum and the 
lateral borders of the collar-like membrane of many of them. 
Proterospongia is of unusual interest since the result of its 
reproductive fission is the formation of a colony whose members 
are united in a mucilaginous zoocytium secreted by themselves. 
In this almost invisible mucus the zooids are wholly immersed 
with the exception of the collar and flagellum, which project 
into the water where the colony freely swims. Before Mr. Ox- 
ley discovered his pedicellata there was but one known species, 
Proterospongia Haeckeli, 8. K. which, so far as I am aware, has 
not been found in our waters, Mr. Oxley’s species differing from 
the latter chiefly in the size of the colonies and in the presence 
of the short pedicle already referred to. This pedicellate form 
I haye recently obtained in considerable abundance, taking it 
about the middle of March from a small pond, in company with 
Lemna, many species of Closterium, diatoms, infusoria and 
aquatic worms. The colonies vary in size from a minute clus- 
ter of three or four members, to floating concayo-convex films 
one-fiftieth inch in diameter and containing thousands of zooids, 
agreeing with Mr. Oxley’s statement that “ the number of indi- 
viduals composing a colony amounted from 10,000 to 20,000 or 
more.” 
