G. rectangulum, dorso arcuato. This gonium is rectangular, the hind-part arched.
This differs but little from the preceding; the angle at the base is a right one, the larger vesicle is transparent, the rest green.
118. Gonium Truncatum.
G. obtusangulum, postice arcuatum. Gonium with obtuse corners, the hind-part arched.
Much larger than the foregoing, the fore-part is a straight line, with which the sides form obtuse angles, the ends of the sides being united by a curved line; the internal molecules are of a dark green, there are two little bright vesicles in the middle; its motion is languid. It is found chiefly in pure water, and that but seldom.
X. BURSARIA.
Vermis simplicissimus, membranaceus, cavus. A very simple, hollow, membranaceous worm.
119. Bursaria Truncatella.
B. ventricosa, apice truncata. Ventricose bursaria, the top truncated.
An animalculum that is visible to the naked eye, white, oval, and truncated at the top, where there is a large aperture descending towards the base; most of them have four or five yellow eggs at the bottom. It moves itself at pleasure from right to left, and from left to right, ascending to the surface of the water in a right line, and sometimes rolling about while descending.