126 



THE HELMINTHES. 



$117. 



cells; in the anterior portion, these cells are more numerous and begin to 

 be surrounded by a granular vitelline substance, in which the primitive 

 nucleated cells are still seen; these cells therefore, ought perhaps to be 

 regarded as germinative vesicles. In front, these eggs, which are of a dis- 

 coidal form, are arranged in a row, or are grouped closely around a rachis 

 which traverses the axis of the ovary. In the Fallopian tube, which may 

 be known by its less diameter, the eggs become more mature, and, having 

 been surrounded by a double colorless envelope, pass into the base of the 

 uterus/-' This last is the largest portion of the genital tube, and is dis- 

 tinguished by its well-marked power of peristaltic action. The vagina, 

 which is distinguished from the uterus by its narrowness and its muscular 

 walls, opens at very difiereut points of the body. Grenerally, as for 

 instance in Ascaris, Spirojjtei-a, Strojigylus, Oxyiiris, Cncullamis, and Tri- 

 chocejjhalus, the Vulva, consisting of a transverse fissure, and often sur- 

 rounded by a very remarkable fleshy swelling, is situated either a little in 

 front of, or near the middle of the body ; but sometimes it opens just in front 

 of the anus.'''' The sperm is usually so accumulated in the bottom of the 

 uterus, that this is probably the locality of fecundation.'^' 



In the males, the posterior portion of this tube is the testicle ; another 

 portion of it, which is short and constricted, is the Vas deferens, which 

 passes into a dilated portion, — the Vesicula seminalis. Usually this last is 

 separated by a constriction from the Ductus ejaculatorius, which opens into 

 another muscular tube (sheath of the penis).''' At the anterior portion of 

 this last, is a horny, copulatory apparatus. The simple or double penis is 

 of variable length, and is protruded by the muscular contractions of its 

 sheath through the external opening, which is always situated at the poste- 



2 The fonnation of eggs in various Nematodes 

 has been «lesci'ibeJ by Siebold (BurUach's l*hys- 

 iul. loo. cit. p. 208), by Bagge (Dissert, de. Sti'jn- 

 pylo, &c., fig. 1-5), and KoUiker {MüUer''s Arch. 

 1843, p. 69, Taf. VI. fig. 20). I have found a 

 rachis in the ovaries of Ascaris aucta, lumbri- 

 coides, mystax, oscu/ata, Cucullanus elegans, 

 and Stronsj/lus inflexus. Tlie eggs of these, 

 while yet immature and flattened, have a point on 

 one of tlieir extremities by which tliey are attached 

 to the racliis. 



With those of Ascaris liimbricoides, this point 

 is very long during a certain period of develop- 

 ment, and the opposite end lias many deep sulca- 

 tions, giving it a remarkable appearance ; see 

 HenU, iu MuUer's Arch. 1835, p. 602, Taf. XIV. 

 fig. 11. 



In tlie mature eggs, which are nearly always oval, 

 it is rare that the double colorless envelope can be 

 clearly perceived.. With Trichosoma, and Tri- 

 chocephalus, there is a short diverticulum at each 

 extremity of the egg. But in Ascaris drtitatii, 

 there is at this same place a long fibrillatrd lihuiiriit; 

 see Mayer, Beitr. Taf. II. fig. 8, and KülliUer, 

 in Mailer's Arch. 1843, Taf. VI. fig. 10-18.* 



•3 Wilh Ascaris dactyluris, CucuUanus ele- 

 gans, Strongylus nodularis, and striatus, the 



borders of the vulva appear quite swollen. With 

 Trichosoma, this swelling is so attached to the 

 vulva as to resemble a prolapsus of the vagina 

 (^Dujardin, Hist. d. Helm. PI. I.). 



With Filar ia attenuata, inßexo-caudata, mihi 

 (from the pulmonary cysts of Delphinus pho- 

 caena), and papillosa (see Leblond, Quelques 

 materiaux pour servir ä I'histoire des Filaires et 

 des Strongles, 1836, PI. II. fig. 1), the vulva is at 

 the side of the mouth. 



With Strongylus paradoxus, it is swollen to the 

 form of a bladder, and is situated near the caudal 

 extremity ; while that of Ascaris paucipara is 

 directly upon the anus. 



4 See Bagge, loc. cit. p. 12 ; and Kölliker, in 

 Muller's Arch. 1843, p. 72. 



5 For the male genital tube, see Mayer, Beitr. 

 Taf. I., and Cloquet, Anat. &c. PI. I. fig. 5, PI. 

 XI. fig. 8. As yet I have observed only a few 

 exceptions to this typical form with male Nema- 

 todes. 



With Filaria attenuata, the posterior portion 

 of tlic testicle is liit'urciitr, and with Ascaris vesi- 

 cularis, there are two moderately large caecal pro- 

 longations which arise from the Vesicula semi' 

 nalis at the place where it empties into the fas 

 deferens. 



* [§ 117, note 2.] Primitively, the ova of Asca- 

 ris consist of nucleolated cells, which are polyhe- 

 dral from mutual pressure. These increase in size 

 gradually, in their passage down towards the ovi- 

 duct, and the granules of the liquid lying between 

 the nucleus or germinative vesicle and the cell-wall 



become developed into cells, and in this way tha 

 mature ova are formed. Probably no better op- 

 portunity is afforded to perceive that morphologi- 

 cally the ovum is at first only a nucleolated or 

 nucleated cell ; see Leidy, loc. cit. p. 43, PI. VII. 

 fig. 14, c. — Ed. 



