Royal Microscopical Society. 
51 
that of the ganglion as well as among those who have it on the 
same side. Besides, there is now a great probability that all the 
Melicertans are dioecious, for they resemble each other so much 
that Mr. Gosse, in the ‘ Popular Science Review/ has proposed to 
reduce the whole family to a single genus. 
To sum up then we may say that the Rotifers can be divided 
into the five families, the Floscularisea, the Melicertadeea, the 
Brachioneea, the Hyclatiniea or Notommatsea, and the Rhilodineea , 
and that among the first four of these five, dioecious genera have 
been discovered. The family of the Rhilodineea is the only one in 
which as yet no males have been found. 
It may possibly still be held desirable to rank the Eotifera 
among the Yermes, with which it must be admitted they have 
many points in common ; but among the reasons for so doing, that 
of their sexual resemblances to the Echinoderms can scarcely hold 
a place. 
Indeed the very peculiar males of the Rotifers lend no little 
assistance to those who, like Gosse and Leydig, would place the 
Rotifera among the Crustacea ; for a parallel case to that of their 
rudimentary condition is only to be found among some of the 
Cirripedes. 
The males of the Entomostraca are often smaller and rarer than 
the females, and (as among the Rotifera) one impregnation suffices 
for a succession of generations of females. There are female 
parasitic Isapods too that have minute imperfect males parasitic 
on themselves; and among the Yermes there are curious rudi- 
mentary males much smaller than the females ; but in all the 
above cases the males possess some sort of mouth and stomach, 
and are capable of taking nutriment, whereas in that of the 
Rotifera, and of the males of the parasitic Cirripedes Alcippe and 
Cryptophialus, the males have not even a rudiment of mouth 
or stomach. As Darwin (in his monograph of the Sessile Cirri- 
pedes) has pithily said, “ they exist as mere bags of spermatozoa.” 
As the male Rotifers spend their short lives in incessantly 
chasing one female after another, they are provided with cilia, 
muscles, eyes, nervous ganglion and nerve-threads (as well as 
with a depuratory apparatus), all of which the males of A Icippe 
and Cryptophialus lack ; but in the remarkable absence of any 
means of procuring nourishment, these Rotifers and Cirripedes at 
the same time most closely resemble each other, and differ from 
almost everything else. 
It is beyond the scope of this paper to discuss the question of 
the affinities of the Rotifers, or that of their true position in the 
animal kingdom ; but I may be permitted to add that there is at 
least one Rotifer — viz. Pedalion — which it seems to be impossible 
to class among the worms, for it has six hollow limbs worked by 
