THE 
MONTHLY MICROSCOPICAL JOURNAL. 
SEPTEMBER 1, 1872. 
I . — On Euclilanis triquetra ancl E. dilatata. 
By C. T. Hudson, LL.E>. 
Plate XXVIII. 
The genus Euclilanis belongs to one of the most fascinating and 
perplexing families of the Rotifers. The members of its various 
species are large, brilliantly transparent, elegant in form, and 
remarkable in structure ; so that it is impossible to find more 
beautiful objects for the microscope than these living atoms. But, 
on the other hand, the species have been badly described and 
wofully confounded together ; several of the genera are hopelessly 
involved one with another, and even the family itself is threatened 
with extinction by a more modern classification than that of 
Ehrenberg. 
Indeed Ehrenberg’s system has so broken down under the 
weight of new discoveries, that I need make no apology for setting 
it aside while attempting to show how the rotifers may be roughly 
grouped, until some really good system of classification has been 
hit upon. 
The most obvious difference of habit among these creatures is 
that some spend the greater part of their lives attached to a plant 
or other foreign body, while the rest generally move freely about 
from one spot to another. This difference would at once separate 
the Tube-formers from the Free-swimmers. 
The “ Tube-formers ” subdivide at once into two groups, viz. 
1st, those in which the mouth is symmetrically situated with respect 
to the body, lying in its longitudinal axis, or the Floscules ; and 
2nd, those in which the mouth is asymmetrically placed, lying on 
the ventral surface, or the Melicertans. 
The Free-swimmers break up into two weH-marked groups ; 
1st, those that both swim and creep like a leech, or the Philodines ; 
and 2nd, those that only swim; and these latter again subdivide 
into a loricated and an illoricated family, to wit, the Hydatines 
and Brachioneans. 
Now, according to the above classification, Ehrenberg’s family 
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