O14 
Photo by} [f. Noad Clark. 
THE GRUB OF THE ARGULUS. 
It is only just hatched, and shows the relatively 
large eyes and barbed hooks which take the place of 
the suckers that appear at a later stage. (Magnified 
fifty times.) 
Marvels of the Universe 
Walls USsISLOUSE, OR AIRGUILUS 
BY FRED. NOAD CLARK. 
Tus creature with the unpleasant name, which one 
associates with another parasite not unconnected 
with the “ genus homo,” is a most interesting 
beast. Unlike the latter, however, it is not, 
technically speaking, an insect, but belongs to one 
of the smaller divisions of the great class Crustacea, 
previously referred to by contributors to this work. 
It is a parasite in the true sense of the term, for 
it derives its sustenance from the living body of 
a “ host,’’ which in the case of the Argulus may 
be the carp, roach, tench, stickleback, and other 
fresh-water fishes. It has been reported to be 
found on tadpoles and minnows, but it was from 
the stickleback that the specimens which are here 
illustrated were obtained. By reason of its excep- 
tional structural character, the elaborate nature 
of its apparatus for attachment to its host, the 
interesting details of 1ts metamorphosis, and the 
curious organs and mode of reproduction, a study of this obscure creature will well repay the 
observer. 
The Argulus may be described as a transparent, jelly-like animal of a greenish hue, the bulk 
of whose body appears as an oval slightly convex shell, which entirely covers the various organs 
which lie on the under surface of the body, with the exception of the swimming feet and so-called 
tail. The female is larger than the male, and an adult measures about one-third of an inch in 
length. 
Photo bu) {/. Noad Clark. 
THE GRUB OF THE FEMALE ARGULUS. 
It has attained the third stage of its existence 
and is rapidly assuming the form of the adult 
state. (Magnified twenty times.) 
It may be distinguished from the latter by the presence of two sharply-defined black spots, 
or ovaries, at the base of the tail-plate. The eyes 
will be seen as two dark masses near the top of the 
body, one of which is shown on page 613, and 
shows its compound nature, similar in structure 
to others of the class, and analogous to the com- 
There are about forty facets 
or lenses in each eye, and they are capable of a 
pound eyes of insects. 
slight rotary twitching movement. A curious feature, 
however, occurs in the existence of a third or single 
eye, situated a little lower down on the middle of 
the back. 
two curious appendages (page 613), tubular in form, 
On either side of the paired eyes are seen 
with a delicately fringed margin and provided with 
At casual sight 
these might be taken for eyes, but are in reality 
muscles for producing a vacuum. 
suckers, by which the parasite is enabled to attach 
itself to the smooth surface of the fish, whilst feeding 
or when depositing eggs on stones or aquatic plants. 
In addition to these suckers, the Argulus is furnished 
with an armament of spines and hooks on the under 
surface of the body, which assist it in retaining its 
