MACAHSTEU — ON ASCAltIS DACTYLT71US. 



2$9 



which is similar to that described and figured in the Appendix to 

 Bagge's " Dissertatio de Evolutione Strongylus auricular is," and 

 ■which has been traced by Diesing in other Nematodes. Mehlis* de- 

 scribes a similar organ as existing in Strongylus hypostoma, but ima- 

 gined he saw it passing as far forwards as the mouth, in which he 

 thought that it terminated ; but this error was corrected by Von 

 Siebold ; and in many of my specimens the character of the external 

 foramen is seen with extreme clearness. This undoubtedly is a glan- 

 dular organ, but of what nature it is hard to say. Mehllsf has put 

 forward a not improbable hypothesis regarding its use, and imagines 

 that it pours out an irritating secretion, which "Stimulates the wall of 

 the intestine of the host, and so causes it to pour out an increased 

 amount of pabulum for the animal's wants : such may be the case, but 

 we have no evidence on the subject. It might perhaps be a rudimentary 

 water-vascular apparatus. 



Enveloping in its convolutions the intestinal canal in the female, a 

 tortuous elongated ovarian tube can be traced (Pig. 2, b) : usually single, 

 though in three of my specimens I found it to be double. It commences by 

 a narrow, but not very sharp-pointed, extremity, which is apparently at- 

 tached slightly to the deep surface of the body wall, near the lower end 

 of the oesophagus ; from this point it courses tortuously, measuring 

 when extended twice or three times the length of the entire body of the 

 animal. At its commencement it contains a finely granular, almost homo- 

 geneous mass, which shortly becomes consolidated into oval vitelline 

 masses, which soon (Pig. 2, k), at a small and very imperfectly marked 

 dilatation in the tube, become perfect ova of a narrow elliptic shape, com- 

 posed of a dark granular, at first obscurely divided vitellus, which occu- 

 pies one half of the bulk of each ovum, and is surrounded by a transparent 

 albuminous fluid, enclosed in a hard casing or shell. These ova are 

 arranged in a single row in the lower or uterine portion of the oviduct ; 

 and occasionally from a rupture of this tube they may be seen floating 

 free in the body cavity of the parent. The perfect ova are not so nu- 

 merous as they are described to be in other species of Ascaris. I have 

 found them to range between twelve and fifty-five in number. The 

 uterine tube, or oviduct, terminates at a small, round, oblique opening on 

 the ventral aspect of the animal, and usually at a point midway between 

 the stomach and the anus (Pig. 2, 1). In case the oviducts be double, they 

 coalesce shortly before they arrive at the vulva. Siebold refers to this 

 opening as being a transverse slit, with swollen margins ; but it certainly 

 seemed to me to be roundish (Pig. 6), and bordered by a slightly pro- 

 minent lip or margin, surrounded by a sulcus. The coats of the duct 

 thicken, and the cavity contracts immediately before it ends at this 

 aperture. When some of these females were left immersed in water 

 for a week, the ova commenced to become developed. At first the eggs 

 were filled with finely granular, irregularly divided vitellus, which 



* Loc. cit., p. 49. t " Isis," 1831, p. 81. 



