422 Wisconsin Academy of Sciences, Arts, and Letters. 
out evertile auricles, but the mastax is so different in these species 
that they do not appear to form a natural group. The genus 
Eothinia is separated from Eosphora on account of the form of the 
mastax, virgate trophi with regularly denticulate rami, because 
this occurs in three species which are very similar in other fea¬ 
tures. A second genus, Besticula, has been created for four species, 
closely related to Eosphora, but with a type of mastax intermediate 
between this genus and Notommata, adapted to prehension, but re¬ 
taining the pumping action unimpaired; there is also close agree¬ 
ment in the form of the body, retrocerebral organ and eyespot. 
The compromise arrived at must be justified by the evidence of 
a common ancestry brought out by a detailed study of each group. 
It is quite true that extreme species often differ considerably in 
their characteristics, but their actual relationship appears in a 
clearer light when the entire series of intermediates are taken into 
consideration. 
There is also something to be said against the very fashionable 
subdivision of existing genera; it may, and if carried far enough 
does, lead to homogeneous and ‘‘natural’’ genera, but this advan¬ 
tage is obtained at the price of a more comprehensive view of the 
actual relationship of the species concerned. A partial remedy is 
then introduced in the form of various higher groupings, tribes, 
sections, etc., but the total gain by this process does not seem to 
justify the more cumbersome machinery and the burden of addi¬ 
tional generic and other names. 
A misleading typographical error occurs several times in volume twenty; on 
page 577, line 22, page 583, line 31, page 585, line 20, page 587, line 7, and 
page 590, line 38, for ramus” read uncus”. 
Subfamily PROALINAE. 
Genus PRO ALES Gosse. 
Notommatid rotifers with spindle-shaped, illoricate body, with 
a slight constriction behind the mastax separating the head and 
abdomen; there is usually a distinct reduction in diameter of the 
body at the base of the foot, which has two very short toes. 
The corona is an oblique disc with well developed marginal cilia 
and two lateral tufts of densely set, long cilia, especially adapted 
to swimming; they resemble auricles, but are not retractile. The 
apical plate is not usually enclosed by the marginal ciliation and 
