Is Pedalion a Rotifer 1 
215 
be closely connected with the integumentary system ; the majority 
of them touch the integument at their extremities only, and more- 
over lie often well away from it, and may be seen now and then to 
hang quite slack, or even to form wide loops; and one, viz. that 
figured at Fig. 2, c, actually traverses two-thirds of the innermost 
portions of the animal’s body, passing from the mid-dorsal line to 
the face of the trochal disk, to which it is attached by a double head. 
Nor is Pedalion the solitary rotifer which refuses to submit to 
this definition. The great majority of rotifers are fairly heterono- 
mous, even as to external shape, and undoubtedly so when both 
external shape and internal organs are taken together. No trans- 
verse section, however thin, of any rotifer that I am acquainted 
with, repeats itself in any portion of the body ; while the distinctive 
feature of a worm is, that transverse sections of definite thickness 
do repeat themselves so remarkably that there seems no reason why 
a worm might not be 6 feet or 6 yards long, instead of 6 inches. 
Besides, in most of the rotifers that I have studied — for instance, 
in Bracliionus, Syncheeta, Pterodina, Asplanchna, Rhinops, Tri- 
arthra, Polyarthra, and others — the main muscles, viz . those for 
retracting the disk, are attached to the integuments at their extre- 
mities only, and freely traverse the perivisceral space, at a good 
distance from the integument. 
As to the possession of “ hollow segmented limbs,” there the 
rotifers have a weakish case ; still it has not been left to Pedalion 
alone to fight the battle for his less-gifted brethren. Synch&ta 
has two hollow rudimentary limbs, each worked by two long 
powerful muscles, attached to spots inside of them, as may be 
seen in my drawings in the fourth volume of this Journal ; and 
by placing these powerfully ciliated limbs at different angles to 
its body, is able to perform many of its curious antics. Triarthra 
and Polyarthra, too, have processes that might pass muster among 
the Greenwich Pensioners ; but I am afraid they do not help the 
case much: Polyarthra, however, has distinct condyles (as Gosse 
has shown), on which its curious processes work ; and Dinocharis 
has equally distinct joints. 
Doubtless all general statements in Natural History must be 
taken with wide allowance ; definitions, classifications, systems are, 
after all, but useful pegs to hang our knowledge on ; and it must 
often be a matter of taste almost, how some odd creature is to be 
ranked and ticketed. If it is desired to establish its genealogical 
relation to* other animals, then indeed the matter ceases to be one of 
taste, and becomes one of intense interest, and one which may well 
give rise to warm controversy; but such discussions I must leave 
to those very few who have the requisite knowledge and capacity. 
I would only venture to hope that, as my readers weigh the various 
