In the Ascaris lumbricoides the penis (a,fig. 94) projects from the anterior part of the anus in the form of a slender, conical, slightly curved process, at the extremity of which a minute pore may be observed with the aid of the micro scope. The base of the penis (b) communicates with a seminal reservoir, and is attached to several muscular fibres, destined for its re traction and protrusion : the reservoir is about an inch in length, and gradually enlarges as it advances forwards : the testis or seminal tube is continued from the middle of the anterior truncated extremity of the reservoir ; it pre sents the form of a long, slender, cylindrical, whitish-coloured tube, extends to the anterior third of the body, forming numerous convo lutions and loops about the intestine, and its attenuated extremity adheres intimately to the nutrient vessels of the dorsal region of the body. The total length of the seminiferous tube in an ordinary sized Ascaris lumbricaides is from} two feet and a half to three feet. Its contents, when examined with a high micro scopic power, consist of a transparent viscous fluid, in which float an innumerable quantity of round white globules, much smaller than the ova in the corresponding tubes of the female. In the genus Trichaccphalus the fila mentary testis is convoluted around the intes tine in the enlarged posterior part of the body. The intromittent organ in the Trichocephalus dispar is inclosed in a distinct sheath, which is everted together with the penis, and then presents the form of an elongated cone (c, fig. 69), adhering by its apex to the enlarged anal extremity of the body, and having the simple filiform spiculum or penis (d,fig. 69) projecting from the middle of its base.
In the Strongylus gigas the bursa or sheath of the penis terminates the posterior extremity of the body, and is a cutaneous production, of a round, enlarged, truncated form, with the spiculum projecting from its centre, as at B, fig. 71. In other species of Strangylus, as in the Strangylus hylexus, the bursa penis is bifid, and in the Strangylus armatus it is divided into four lobes: the obvious functions of these appendages, as of the lateral alwform cuta neous productions which characterize the Phy salapterx and Spiroptcr.e is to embrace the vulva of the female, and ensure an effective intromission and impregnation of the ova.
In the genus Cucullanus, and in most of the smaller species of Ascaris, the intromittent organ consists of a double spiculum.
This is also the case in the Syngamus tra chcalis, the parasitic worm before alluded to as infesting the trachea of the common fowl, and occasioning the disease termed the Gapes? In this species the male individual appears as a branch from the body of the female. The testis begins near the middle of the oesophagus by a slender blind extremity, and winds round the gut, as it descends, gradually enlarging, to the lower part of the intestine, where it sud denly contracts and runs down, as a very slender canal, to near the vulva. It is partly covered by two long slender bodies of a horny sub stance, representing a bifurcate penis.
From this comparison of different genera of the Netnatoidea, it is seen that, although there are many varieties of structure in the efferent and copulative part of the male gene rative apparatus, the essential or secerning por tion uniformly consists of a single tube. A like uniformity of structure does not obtain in the essential parts of the female organs : in a few instances the ovary is single, correspond ing to the testis in the male, but in the greater number of the Nematoid worms it consists of two filamentary tubes.
The Strongylus gigas is an example of the more simple structure above alluded to. The single ovary commences by an obtuse blind extremity close to the anal extremity of the body, and is firmly attached to the termination of the intestine; it passes first in a straight line towards the anterior extremity of the body, and when arrived to within a short distance from the vulva, is again attached to the parietes of the body, and makes a sudden turn back wards fig. 95); it then forms two long loops about the mid dle of the body and returns again forwards, suddenly dilating into an uterus (e), which is three inches in length, and from the anterior extremity of which a slender cylindrical tube, or vagina, about an inch in length, (e,d, fig. 95) is continued, which after forming a small convolution ter minates in the vulva, at the distance of two inches from the ante rior extremity of the body. Rudolphi was uncertain as to the ter mination of the ovi duct in the Strongylus gigas, and Professor Otto, who appears to have mistaken its blind commencement for its termination, believed that the ov i du ct opened into the rectum.
The theory which had suggested itself to Rudolphi of the corre lation of a simple ovi duct in the female with the spiculum simplex of the male, and of a double oviduct with the spiculum duplex, receives additional dis proof from the circumstance of the uteri and oviducts being double in the Strwigylus in jlexus and Strongylus ormolus. In the former species (which infests the bronchial tubes and pulmonary vessels of the Porpesse, and which I once found in the right ventricle of the heart of that animal,) each of the two female tubular organs may be divided into ovary, oviduct, and uterus : the ovary is one inch in length, commences by a point opposite the middle of the body, and, after slightly enlarging, abruptly contracts into a capillary duct about two lines in length, which may be termed the oviduct, or Fallopian tube, and this opens into a dilated moniliform uterus three inches in length ; the divisions here described were constant in several individuals examined, and cannot, therefore, be considered to result from partial contractions. Both tubes are remark ably short, presenting none of the convolutions characteristic of the oviducts of Ascaris and Filaria, but extend, in a straight line, (with the exception of the short twisted capillary communication between the ovaria and uteri,) to the vulva, which forms a slight projec tion below the curved anal extremity of the body.