THe Microscope, 261 
chiefly to call attention to the statoblasts. That the reader may 
determine the genus to which his Polyzoan specimen may belong 
there is here reproduced, with a few changes, a Key which the 
writer originally published in The Journal of the Trenton Natural 
History Society for January, 1887, and which the editor of The 
American Monthly Microscopical Journal republished in June, 1888. 
KEY TO GENERA OF FRESH-WATER POLYZOA. 
§ Colonies formed of chitinous cells (a). 
§ Colonies formed of gelatinous tubular cells (b). 
§ Colonies a jelly-mass surrounding the polyps (c). 
‘a Cells urn-shaped; lophophore subcircular; colonies 
PENGEHU Ny. Sats Dt)! SS) Onatelias ae 
a Cells tubular; lophophore hon hae shaped, . Plumatella. 
a Cells “anoiben lophophore circular or oval, . . Fredericella. 
@ Cells clavate, growing end to end; iohaolore cir- 
CUIAEY cc's Peet lle soo Sone va, eee ae 
b Branches not attached; lophophore horse-shoe 
sinaipeds. 4 bt. 2 Bs te ds, - Elyalinelion 
Colonies more or less elobuben hertentle fixed (d). 
¢ Colonies oval or elongate, slowly travelling, . . Cristatella. 
da Colonies sacciform, finally lobed or branched. (Not 
found in this countryJees ~~: 6... Ss we, OO RepU 
dad Colonies globular, orifices grouped in lobed areole, 
Pectinatella. 
One form of reproduction among the Polyzoa is by means of 
what are called statoblasts, or “ winter eggs,” because, being pro- 
duced in the autumn, they remain unchanged through the 
winter, giving exit in the spring to the ciliated embryo that shall 
finally develop into the Polyzoan. It is these statoblasts that 
are so often seen as dark brown little bodies, thickly studding 
the surface of the half dead masses of Pectinatella jelly in Sep- 
tember or later, and floating on the water, where they are fre- 
quently captured by the collecting microscopist. 
Although small, the largest measuring perhaps 1-30 inch in 
diameter, their rich, dark brown color makes them easily visible, 
especially when in any abundance. As already stated, they are 
sometimes gathered with other aquatic objects and may be the 
cause of considerable mental trouble to the collector before he 
earns their source and meaning. 
