142 



ENTOZOA. 



Fig. 96. 



Female organs, 

 Ascaris Iwnbricoides. 



testine and dilates into the 

 uterus (k, fig. 96). The 

 division of this part soon 

 takes place, and the cornua 

 extend with an irregularly 

 wavy course to near the 

 posterior extremity of the 

 body, gradually diminish- 

 ing in size; they are then 

 reflected forwards and form 

 numerous, and apparently 

 inextricable, coils about 

 the two posterior thirds of 

 the intestine. Hunter has 

 successfully unravelled 

 these convolutions, and 

 each of the tubes may be 

 seen in the preparation in 

 the Hunterian Collection 

 to measure upwards of four 

 feet. The generative organs 

 contained in the female, or 

 longer branch of the Syn- 

 gamus trachealis. have a cor- 

 responding structure with 

 those of the Nematoidea. 

 The capillary unbranched 

 ovary and uterus are double, 

 as in Ascaris, Spiroptera, 

 Filaria, and most Stron- 

 gyli. The vulva is in the 

 form of a transverse slit, 

 and is situated at the ante- 

 rior third of the body, im- 

 mediately below the attach- 

 ment of the male branch. 



In the Nematoidea the 

 male individual is always 

 smaller, and sometimes dis- 

 proportionately so, than the 

 female. At the season of 

 reproduction the anal ex- 

 tremity of the male is at- 

 tached to the vulva of the 

 female by the intromission 

 of the single or double spi- 

 culum, and the adhesion of 

 the surrounding tumid la- 

 bia; and, as the vulva of 

 the female is generally si- 

 tuated at a distance from 

 either extremity of her body, 

 the male has the appearance 

 of a branch or young indi- 

 vidual sent off by gemma- 

 tion, but attached at an 

 acute angle to the body of 

 the female.* 



In the Heterouru andro- 

 phora of Nitzch (Hersch 

 and Griiber's Encyclopae- 

 dic, th. vi. p. 49, and th. ix. 



* See Figures of Nematoid 

 Entozoa in copulation, in 

 Bremser, Icones Helminthum 

 tab. iii. fi^. 8. 15. ; and Guiit, 

 Lehrbuch der Patholog : Ana- 

 tornie der Haus-Saugethiere, 

 tab. vi. fig. 35. 



taf. 3. f. 7.) the male maintains an habitual con- 

 nexion with the female, which has a horny pre- 

 hensile process for tiie purpose of retaining the 

 male in this position. Here there is no conflu- 

 ence of the substance of the bodies of the two 

 sexes ; the individuals are distinct in their su- 

 perficies as in their internal organization. But 

 this singular species offers the transitional grade 

 to that still more extraordinary Entozoon, the 

 Syngamus trachealisy in which the male is orga- 

 nically blended by its caudal extremity with the 

 female, immediately anterior to the slit-shaped 

 aperture of the vulva, which is situated as usual 

 near the anterior third of the body. By this 

 union a kind of hermaphroditism is produced ; 

 but the male apparatus is furnished with its 

 own peculiar nutrient system ; and an indivi- 

 dual animal is constituted distinct in every 

 respect, save in its terminal confluence, with 

 the body of the female. This condition of 

 animal life, which was conceived by Hunter as 

 within the circle of physiological possibilities, 

 (see Anim. (Economy, p. 46,) has hitherto been 

 only exemplified in this single species of Ento- 

 zoon ; the discovery of the true nature of which 

 is due to the sagacity and patient research of 

 Dr. Charles Theodore Von Siebold. 



The Entozoa of the parenchymatous class 

 are chiefly oviparous, those of the cavitary class 

 for the most part ovoviviparous. 



The germinal vesicle has not yet been dis- 

 covered in the vitelline substance of the ova 

 of the Acanthocephala, Trematoda, or Ces- 

 toidea; but it is distinctly discernible in the 

 ova of the Nematoidea ; I have also observed 

 and have figured it in the highly organized 

 ovum of the Lirjguatula ttenioides. 



The ova of the Teenies present considerable 

 varieties of size and form in different species ; 

 Rudolphi has figured seven forms of these 

 ova in the Synopsis Entozoorum, (tab. iii.)* 

 Some are much elongated and pointed at both 

 extremities, others elliptical: the ova of the 

 Bothriocep/ialus Latus are of the latter form, 

 f C,/g 89) ; those of the Ttenia solium are sphe- 

 rical, as are also the ova of Tteniafiiiformis. 

 In some species the development of the em- 

 bryo Tape-worm has been observed to have 

 distinctly commenced in the undischarged ova, 

 as in tSie T<enia polymorpha. In dissecting a 

 Touraco infested by the Tania jUifbrmis, we 

 found that the segments of the Taania in which 

 the ova were most developed had been t.e- 

 tached from the rest of the body, a process 

 remarkably analogous to that which takes place 

 in the Lernete and Ent.anostraca, where the 

 external ovaries are cast off, when charged with 

 mature ova. 



A few of the Trematode Entozoa, as the 

 Monostoma mutabile, produce the young alive ; 

 but these have a very different form from the 

 parent. It would seem that they were des- 

 tined to pass a transitional state of their ex- 

 istence in a fluid medium permeated by light, 

 since two coloured ocelli have been discovered 

 on the head, and the surface of the body is 

 beset with locomotive vibratile cilia. f 



* Synopsis Entoz. p. 505, pi. iii. fig. 10, 11. 

 t See Siebold, in Weigmann's Archiv. 1835. 



