416 Wisconsin Academy of Sciences, Arts, and Letters. 
general idea in so far as it could be done without violating accepted 
principles of classification and with proper deference to the neces¬ 
sarily hypothetical nature of present-day ideas of the interrelations 
of the various rotifer groups. 
The family Notommatidae may then be characterized as a family 
of ploimate rotifers with moderately elongate, prismatic or spindle- 
shaped, illoricate or partially loricate body, ending in a short, nor¬ 
mally two-jointed, tubular foot with two toes, in rare cases fused; 
w^th a corona composed of simple cilia, primarily forming a mar¬ 
ginal wreath composed of strong cilia adapted to the propulsion of 
the animal, and enclosing the unciliated apical plate and a buccal 
field with short cilia for bringing food to the mouth, which is near 
the ventral margin of the corona; the ciliation may be continued 
beyond the mouth as a so-called chin. The mastax is a more or 
less specialized form of the malleate type, and we have divided 
the family into six subfamilies, according to the degree of de¬ 
parture from the type. The stomach and intestine are usually 
without distinct separation; the ovary is nearly always an irregu¬ 
larly oval, disc-shaped organ with the normal number of nuclei, 
eight; the excretory system consists of two lateral canals with 3-5 
flame cells, opening into the bladder, which is either an expansion 
of the cloaca or a separate, pyriform vesicle discharging into the 
cloaca through a short duct. The ganglion is large and saccate; 
the retrocerebral organ is very unequally developed in the different 
genera. The eyespot is usually cervical, but may be frontal or 
absent. 
The subfamily Proalinae is characterized by a type of mastax 
very closely related to the malleate; the unci are adapted to the 
crushing or grinding of the food; a weak ‘ ‘ piston ’ ’ is usually pres¬ 
ent, but it is attached to the ventral floor of the mastax, and not 
to the fulcrum. The retrocerebral organ is absent or limited to a 
rudimentary sac. 
The subfamily Notommatinae has a mastax to which De Beau¬ 
champ applied the name virgate, first used by Hudson and Gosse 
with ambiguous definition; it is characterized by the development 
on its ventral surface of a powerful muscle, the hypopharynx, 
attached to the fulcrum and acting as the piston of a pump, the 
entire mastax forming the cylinder of the “pump”, thus enabling 
the animal to extract the contents of plant cells or of the bodies of 
small animals without swallowing them. A well-developed retro¬ 
cerebral organ is present in the majority of the genera. 
