The ova of the Linguatula are of an oval form : the germinal vesicle is situated near the superficies half-way between the two extremi ties; the vitt:Hine membrane is surrounded with a strong cortical membrane : the develop ment of the rictus takes place out of the body. In the Strotwilas gigas, Strongylus injlexus, and a species of Tmchosoma infesting the in testines of the Goatsucker, we have found the flews completely formed in the ova contained in the uterus or terminal segment of the gene rative tube, while those in the ovary or narrow commencement of the same part weie still occu pied with the granular matter of the vitellus The mature ova of the StronKylux gigax are of an elliptical form, and the embryo within is plainly seen coiled up through the trans parent coats of the egg; the resemblance which these bear to the Trichina when inclosed in its inner cyst is very striking: the hypothesis suggested by this resemblance need only be alluded to for the purpose of exciting the at tention of those, who may hereafter meet with the preceding minute muscular parasite, to the existence of larger Nematoid Entozoa in other parts of the body.
Cloquet describes the ova in the beginning of the ovaries of the Ascuris Lumbricoides as consisting of rounded linear corpuscles, pointed at one extremity, thickened at the other; in the middle of the ovaries they as sume an elongated triangular form, and one of their angles frequently supports a small spherical eminence; the base of the ovum adheres to the parietes of the oviduct, the apex projects into its cavity. In the enlarged canals, which he terms the cornua of the uterus, the ova are unattached and of a conoid or irre gularly triangular figure. In the uterus itself they have assumed an ovoid or elliptical form, are surrounded by a transparent glairy mucus, and are composed of a transparent cortical membrane, perfectly smooth on the external surface, and filled with a transparent fluid, in which floats a linear embryo, disposed either in a straight line or coiled up. Cloquet never observed the young Ascarides excluded from the egg in the interior of the uterus, and we equally searched in vain for free embryos in the generative tubes of the Strongylus and Oxyurus above-mentioned, although their de velopment in regard to form appeared to be complete in the ovum ; the structure of the embryo resembles that of the simpler Vibriones,• there being no generative tubes apparent, and the cavity of the body being occupied by a granular parenchyma.
With respect to the exclusion of the ova in these and similar ovoviviparous Nematoid Entozoa, it would appear to be very commonly accompanied with a rupture of the parietes of the body and of the generative tube. Ito dolphi observes, with respect to the Cucullanns, " Ovula, verine quieto, per intervalla ex vulvil pullulent ; quip eodem disrupto, quod swpe accidit, ovula vel embryones ex ovariis pro lapsis parituque ruptis vi qutidam et undatim protroduntur."
The generation of the Filaria Illedincnsis is Of the viviparous kind, and the progeny is countless,—" Pitlirtiai nostrw," observes Itudol phi, " prole quasi farctm stint, quod si harum longitudinem illius vcro minittiem spectas, fcetuum mu!ta inillium millia singubs tribuit." What is most remarkable is, that these em bryos are not, as in the Strongylus and the Nematoid genera above-mentioned, enveloped in an egg-covering, 'nor are they included in a special generative tube, but float freely along with a granular substance in the common mus cular envelope of the cavity of the body.
M. Jacobson,* who has recently published a description and figures of the young Filaria Medinensis, compares the body of the mother to a tube or sheath inhabited by the young ones; and, after a careful examination of three individuals, we have equally failed in detecting either generative or digestive tubes within the muscular sac of the body. The external tunic of the body is a firm subtransparent elastic integument, which, examined under a high magnifying power, presents fine trans verse stria`, occasioned most probably by ad herent muscular fibres. Within this tunic and readily separable from it are the longitu dinal muscular fibres, which are arranged in two fasciculi, separated from each other by two well-marked intervals on opposite sides of the body, which are indicated by an impression (or furrow, as the worm dries by evaporation) on the exterior surface. When from long maceration the crisp outer integument has become separated from the longitudinal mus cular bands, these might be mistaken for two tubes contained loosely within the cavity. I believe that these muscular bands are the tubes fibrineuses, described by Dr. Le Blond t as the alimentary canal and intestine in the fragment of Filaria Medinensis, which he dissected. In a small Filaria Medinensis, containing no vermiculi, we have also failed to discover any distinct tubes for digestion or generation.
It is interesting to observe that the young of the Filaria Medinensis do not resemble the parent in form; one extremity is obtuse, the body slightly enlarges for about one-fourth of its length, then gradually diminishes to within a third of the opposite extremity, which is capillary and terminates in the finest point. The enlarged part of the worm contains a granular substance, and is coiled upon itself, and presents a distinct but minute annulation of the integument : the capillary extremity is smooth, transparent, and generally straight. The Trichocephalus dispar closely resembles in its external form the foetus, if it be such, of the Filaria Medinensis.