632 Wisconsin Academy of Sciences, Arts, and Letters. 
mallei, there is a rather complex supplemental oral armature; 
two thin, trapezoidal plates with upturned external and posterior 
edges are superposed on the rami and meet at the inner posterior 
angles; at the anterior angles are hinged two curved rods, slightly 
expanded at the opposing anterior ends. The function of this 
complicated apparatus is no doubt to enlarge the oral opening; 
the food of the animal consists mainly of desmids and it is able 
somehow to swallow entire the very large Micrasteiria torreyi, which 
is often found unbroken in the stomach. An enormous piston 
very nearly fills the entire interior of the mastax; while it is 
bulky, it seems to be very weak, and the points of attachment of 
the feeble muscles have not been definitely ascertained. It is 
certain, however, that the powerful muscle attached to the fulcrum 
in the normal virgate mastax plays but a very subordinate role in 
this instance, which fact is clearly indicated by the small size of 
the fulcrum. 
The oesophagus is very long and muscular and is capable of 
being greatly distended. The gastric glands are elongate, con¬ 
stricted near the middle, and strongly curved, so that in certain 
positions four glands appear to be present. The stomach and 
intestine are separated by a relatively long, tubular constriction; 
the walls of both are syncytial, and the only provision for storing 
food reserves is a single ring of spherical cells, attached by a 
slender tube to the walls of the stomach at the opening of the 
tubular constriction. The ovary is very long, slender, and rib¬ 
bon-like, and contains from 20 to 30 nuclei. The spinous eggs 
seen by Hudson are without doubt the ordinary summer eggs 
and not the resting eggs; the hooked spines serve to attach them 
to the water plants. The bladder is large. Four pyriform foot 
glands of nearly equal size are present. 
The retrocerebral sac is small, projecting but little beyond the 
ganglion; the subcerebral glands are nearly twice as long, slender, 
and pyriform; they do not contain bacteroids. The eye-spot is 
large. 
Total length 750-1000y; toes 60-80/z; trophi 80/l. 
Tetrasiphon hydrocora is rather rare and seems to be limited 
to non-calcareous regions with very soft, acid waters. It is nearly 
always covered with a very firm jelly-case, much more resistant 
than the protective covering of any other rotifer except Notom- 
mat a peridia, and almost rivaling the egg-cases of the pond-snails 
in toughness. 
