EXTRACTS FROxM: FOREIGN PERIODICALS, 
97 
vinced M. Duges, that it is not excess of food, but numerous eggs, which cause 
the insect to remain so long in its cell. Are these eggs—which are distinct and 
numerous—hatched under the skin ? Are they laid there ? That seems impos¬ 
sible ; and if they are dropped from the side of the anus, it would only be to fall 
outside. Possibly, it is true, the mother rnay die before laying, and the 
little vermiform larvae may produce an ulcerous abscess in the part ; they would 
then be no longer able to breed, in consequence of the injuries they are supposed 
to cause. Animals infested by this insect are unable to get rid of it, and yet the 
effects of such attacks are seldom serious.—The legs do not differ much from those 
of the Common Flea (P. irritans)^ but the thorax has no comb, nor membranous 
or villous fringe. The head bears considerable resemblance in shape to that of 
P. irritans^ and is likewise destitute of spines; the eye is large; antennae 
lenticular, oval, keeled; the sucker is comparatively large, and M. D. mentions 
some particulars relative to this organ which, for want of space, we must omit.— 
The jaws are short, and only differ from those of the Common Flea by the first 
and second articulations being nearly of equal length. The chief distinctions 
appear to lie in the formation of the antennoe, the lips, and the palpoe, and although 
these are amply sufficient to characterise the species, we think, with M. Puges, 
that the insect above described has no claims to rank in a separate genus, but must 
still retain its name of Pulex penetrans. 
2. Organs of Sensation of Pentastoma toenioides. —A remarkably well 
developed nervous system exists in this reptile, as indeed Cuveir has already 
pointed out. When the back of the animal is cut open, and the brown strings 
forming the ovary are taken away, the intestinal canal is exposed to view; when 
again this is extracted, we find under the oesophagus a long, thin, white ganglion 
‘—the cerebral ganglion—situated above the sexual apparatus. This ganglion 
sends out on all sides fine threads, amongst \Vhich are especially observed, from 
their size, the two which pass to the anterior extremity of the body; they supply 
several very slender threads to the oesophagus, and terminate in the lateral cavities of 
the mouth, or at the holes containing the fangs. The ganglion moreover transmits, 
to the posterior portion of the body, two nerves which extend along the open¬ 
ings of the cells formed by the passages in the leaflets described in a former part of 
this paper; the}?' are attached to the walls of the abdomen. These nerves pre¬ 
sent neither swellings nor points of union with one another; their course is not 
in a straight line, but slightly tortuous, so that each nervous filament penetrates, 
with a flexure, into the openings before mentioned.—Thus it will be perceivedj 
that the nervous system of this intestinal worm is distinguished from that of Am- 
phistoma subtriquetrum^ by the latter possessing, under the oesophagus, two 
ganglions communicating with, each other by means of a nervous cord, and by the 
1^9. 8, Vol.IL 0 
