Leuckart looks upon these worms as females, and their reproduction as parthenogenetic. Schneider considers that the male exists by the side of the female sex, and that they are consequently hermaphrodites. These
worms in the lungs are viviparous, and embryos are found in the midst of the intestine of the same animal which gives lodging to the female. These same worms, proceeding from an hermaphrodite parent, or from parthogenetic females, live at liberty, and not parasitically in damp earth or in a decomposed body, and differ from their parents in size as well as in sexual organs. They all become either male or female, and consequently their fecundity is dependent upon copulation. Their parents could all multiply without it, but they cannot. The females alone produce a new generation.
A worm known by the name of Vibrio anguillula lives in grains of corn while still green, and multiplies there to a prodigious extent; it is this which causes the disease known by the name of smut. The grains grow hard, and enclose nothing but little dried worms, which remain thus without apparent life, yet without dying, until they are moistened, when they become damp, the tissues swell, the organs resume their natural appearance, and the functions are restored at the end of a few hours.
In a grain of corn affected by smut, anguillulæ without distinct organs are found, which may be dried and revived eighteen times in succession, according to Mons. Duvaine, who thinks that these anguillulæ, leaving an infected grain, come out of their envelopes in a field of corn, cling to the young stalks, and rise with them. They begin to develop themselves in the rudimentary flower of the corn, and acquire genital organs like nematodes. Males and females are always found separately in a grain of corn.
The ermine lodges in its lungs and tracheal artery
a long worm, to which I have given the name of Filaroides mustelarum. It usually forms a little sac, which resembles a tubercle. Many individuals of different sexes, wound round each other, are so closely tied together that they can with difficulty be separated. They resemble a ball of cotton. This filaroid sometimes gets into the frontal sinus, and mechanically destroys a part of its osseous walls, so that the skull is pierced by a hole above the frontal sinus. Dr. Weyenberg made this observation.
It is probable that other species of Mustela will present the same phenomena, for the skulls of this animal are often to be found perforated above the orbital cavity.
The Ollulanus tricuspis is a worm which lives in the walls of the stomach of cats; it is viviparous, and the young ones sometimes wander into the muscles of their host. But the natural course of things is that the young are evacuated with the feces, and that these dejecta, according to all probability, form part of the food of mice, and pass with them into the cat. It is to be hoped that Leuckart will soon put this migration out of doubt by a decisive experiment, and will prove that the mouse serves as a vehicle for three different worms, the Cysticercus, the Spiroptera obtusa, and the Ollulanus tricuspis.
Many nematodes lodge in the substance of the walls of the gizzard of birds. In the large goosander we have found one which has round its head four blades, crossing each other, toothed on the concave side. We have given the name of Ascaracantha tenuis to this worm. It has very small eggs. The Trichosomum crassicauda is a
nematode of the rat; the female is 2·5 millimètres in length, and the male ·17 millimètres, and it lives in the uterus of its female. Five males are occasionally found in one female. This observation made by Leuckart has been confirmed by Bütschli. The male has its digestive tube incomplete; its female feeds for it.