1884. ] Notices of some new Parasitic Inufusoria. 1085 
extremity of the posteriorly projecting portion suddenly acuminate. Length of, 
body yyy inch. Habitat, the rectum of the spade-foot hermit toad, Scaphiopus hal- 
brooki, 
Another infusorian, which lites more or less in the light of 
the sky, but suffers and often dies when forced to leave its host, 
occurs not uncommonly as an ectoparasite on the social rotifer 
Megalotrocha. I have taken it in considerable numbers on col- 
onies obtained from widely separated localities and at long in- 
tervals. This season the rotifers have seemed especially abund- 
ant and the colonies particularly luxuriant. The infusorian 
glides rapidly over the surface of the host, often passing from 
one individual to another, and running to the edge of the ciliary 
disc, whence a current from a neighboring rotifer occasionally 
Sweeps it into the surrounding water. If carried so far beyond 
the influence of the currents that it fails to find its way back to 
the colony, it soon begins to show evidence of uncongenial sur- 
foundings. Its form changes, it becomes swollen, pale and 
ghostly, its cilia act irregularly and the creature speedily dies, the 
rotifers’ cuticular secretions seeming necessary for its welfare. 
The ectoparasite referred to belongs to Stein’s Hypotricha and 
to Ehrenberg’s genus Chilodon. It differs from the cosmopoli- 
tan Chilodon cucullulus (Mull.) Ehr., in form and size, in the 
absence of the sharply pointed anterior extremity or lip, in the 
greater curvature of the pharynx, in the course of the adoral 
channel, that of C. cucullulus being directed forward and out- 
ward from the pharyngeal orifice, and especially in its ectopara- 
sitic habits. The convexity of the dorsal surface varies. In 
Some individuals it is evenly rounded; in others conspicuously 
flattened and often traversed by irregularly transverse grooves or 
channels, The curvature of the pharyngeal armature is also 
variable, 
When the parasite is gliding over the host's surface it is not 
Possible to observe the manner of taking food. But individuals 
having been swept into the water and been brought back by the 
return current, have occasionally settled on the cover- glass in 
Such a position that the process was apparent. When feeding 
from the side of a rotifer or from the retracted and rounded 
extremity, the anterior end becomes much narrowed and elon- 
Sated, while the pharynx is protruded and closely applied to the 
Surface which it infests, 
