ROTATORIA. OP THE UNITED STATES. 
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colored than those of the stomach, but there is no precise line of demarcation between 
the two. The intestine narrows rapidly to end at the anus, which lies beneath the 
edge of the lorica, .just above the beginning of the foot, a little to the left of the 
middle line. 
Food of the Rattulidce. — The food of the Rattulidce seems to consist chiefly of 
small particles suspended in the water, which are brought to it by its cilia, or of the 
floccose material covering the surface of water plants. The animals may often be 
seen creeping over the stems or leaves of water plants with the corona against the 
surface, as if they were feeding, but it is very rarely that one sees any definite 
namable thing devoured. In one case, and one only, I have seen a Raitulus display 
predatory tendencies. A Rattulus gracilis Tessin seized a young Diurella tenuior 
Gosse, which happened to be near it, pierced the lorica with its jaws, tore out a 
piece from the side of its prey, and devoured it. The jaws of many other species 
seem better fitted, for carnivorous habits than do the comparatively weak ones of 
Rattulus gracilis Tessin, but I have seen no other instances of the character just 
described. 
(2) Brain. — The brain in the Rattulidce is usually a large, oblong body, rather 
prominent, which lies on the dorsal side of the mastax, in the anterior part of the 
body. In front the brain has no defined boundary, merging into the mass of sub- 
stance which supports the corona. Its main mass frequently lies to the left of the 
striated area or ridge on the lorica. The brain is usually somewhat shorter than 
the mastax, but in a few cases — notably in Diurella stylata Eyferth — it forms a very 
large sac, extending backward more than half the length of the lorica (hr., pi. hi, 
fig. 27). In such cases the brain is seen to be made up of large cells, whose outlines 
are clearly distinguishable. 
In the Rattulidce the brain has no opaque, chalky mass at its posterior end, such 
as is found in many of the Notommataclce. Gosse (1889) described as Rattulus 
cirnolius an animal in which the brain has such a chalk mass, but from Gosse’s 
description and figure (see p. 342 and fig. 138, pi. xv) it seems clear that this animal 
was not one of the Rattulidce; it should rather be classed with the Notommataclce. 
Connected with the brain is the single eye. This is a hemisphere of red pigment, 
usually attached to the posterior end or under side of the brain. In a number of 
species the brain is divided at its posterior end into two unequal lateral lobes', the 
left one being smaller and bearing the eye at its tip. This condition is shown in fig. 
99, pi. xi (Rattulus lophoessus Gosse), and in figs. 102 and 103, pi. xii (R. elongatus 
Gosse); it is present in a number of other species also. The dorsal antenna is 
connected with the brain by a slender cord, which is very evident in Rattulus 
cylindricus Imhof (pi. vii, fig. 63). It is probable that the lateral antenme are thus 
connected with the brain also. From each of these there passes forward a slender 
cord , but I have not succeeded in tracing this to the brain. 
(3) Excretory organs. — The excretory organs do not differ essentially from 
those found in other rotifers and are not strikingly developed in the Rattulidce, so 
that this group is not a favorable one for their study. For this reason I have not 
paid especial attention to the excretory system. It consists essentially of the well- 
known lateral canals, one on each side, which open at their posterior ends into a 
small bladder-like structure, the contractile vacuole. These parts are shown in fig. 
24 (pi. n) and fig 32 (pi. hi). 
