

EXTRACTS FROM 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 may die befoi-e 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 antennae, the lips, and the palpae, and although 

 these are amply sufficient to characterise the species, we think, with M. Duges, 

 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 which 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 ; they 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 perceived, 

 that the nervous system of this intestinal worm is distinguished from that of Am- 

 pliistoma subtriquetrum, by the latter possessing, under the oesophagus, two 

 ganglions communicating with each other by means of a nervous cord, and by the 

 No. 8, Vol. II. o 



