118 



THE IIELMIXTHES. 



^113 



CHAPTER Yin, 



ORGANS OF SECRKI'ION. 



§ 113. 



No orga is of secretion have been found, except in the Trematodes and 

 Nematodes. In most of the Trematodes, there is, upon the median line of 

 the posteriDr part of the body, a contractile sac, which usually opens out- 

 wards, '^^ at the caudal extremity, and seldom at the posterior part of the 

 back.*-' This sac is single, <■''' bifurcate,*^' or multiramose. In the last case, 

 its branches are spread usually over the whole body/'' Its walls are quite 

 thin, and therefore, it is seen with difficulty when wholly contracted or 

 empty. It contains a colorless liquid filled with numerous granules or 

 vesicles, which, during the contractions, pass up and down, or escape 

 through the external opening.*''' This organ is sometimes so crowded with 

 clear, solid corpuscles, composed apparently of earthy matter, that exam- 

 ined by reflected light, it has a cretaceous aspect.*'^' 



In many Nematodes, there is on the ventral surface and at a variable 

 distance from the head, a small oblique opening surrounded by a sphincter. 

 In some species, two canals pass from it and run backwards on each side 

 of the intestinal canal ; and in others, there are also two other canals which 

 extend forwards in the same way. The use of the colorless and homoge- 

 neous secretion of these organs is yet unknown.***' 



1 This opening, known as the Foramen caudate 

 with Distomu7n, Holontomuni, Monostomum, 

 Aspidoganter, and Diplostomum, has formerly 

 been cumparefl to an anus by Nardo (Heusin- 

 ger^s Zeitsch. für organische Phys. 1827, I. p. 68), 

 and by Baer (Ibid. II. p. 197). Mehtin (Observ. 

 de Distomate,p. 16) having shown that it belonged, 

 in DistomuTK hepaticum, to a particular organ 

 ■which is ramified like a vessel, has properly re- 

 jected this analogy ; see Isis, 1831, p. 179. With 

 the larvae of Trematodes, known as Cercaria, 

 Bucephalus, and Distomum duplicatum, the 

 base of the tail is thrust into the excretory opening 

 of this organ, and its contents cannot escape until 

 the animal has lost the tail. 



2 Amphistomum. 



3 Monnxtomum faba, Dixtomum cirrisferiim, 

 Gasteroxtominn Jimbriatum, and Bucephalus 

 jiolymorphus. 



4 Distomum chilostom.um, claviserum, lima, 

 maculosum, tereticolle, varieiratum, and many 

 species of Monostmnum, — where the two closed 

 ends of the sac often extend to the cephalic ex- 

 tremity. With Distomum appendiculatum , the 

 two branches of the excretory organ utiite directly 

 behind the oral sucker. With Aspidoi^aster coii- 

 chicola, it divides into two canals near the Fora- 

 men caudate, which extend to the anterior ex- 

 tremity. Ill Amphistomum, two similar canals 

 wind from the head along each side of the body, w 

 the middle of the posterior back, where they open 

 outwards, after having formed by reunion a pyri- 

 form reservoir. Laurer (De Amphistomo conico. 

 ji. 10, fig. 22) has given a figure of this reservoir, 

 in which he ha^! confounded the secretory canals 

 with the nutritive vessjls. 



5 Beside Distomum, hepaticum, Holostomum. 

 urni^erum, the Distoma also with a spinous 

 head, have a widely-ramified excretory organ ; see 

 Mehlig, Isis,1831, p. 182. 



6 With the spinous-headed Distommn militare, 

 and echinatum, this organ is often so reduced in 

 substance, that here and there are perceived only 

 isolated groups of the ramified canals. 



7 The solidity of tliese corpuscles may have been 

 the reason why Ehrenberg (Symb. Physic. Anim. 

 Evertebr. Ser. I. Phytozoa entozoa) has taken those 

 of Cercaria ephemera for eggs, and the two canals 

 of the excretory organ for ovaries ; and why 

 Nordmann (Microgr. Beitr. lift. 1, p. 54, Taf. I. 

 fig. 7) has regarded their escape from the body 

 with Distovium annuligerum, as an act of ovi- 

 position. 



The corpuscles of this kind found in the excretory 

 organ of certain Trematodes, as for instance in a 

 larva of Monostomum known as Cercaria ephem- 

 era, remind one from their astiect, of the small 

 cilcarcous subcutaneous bodies of many 'V'ae/ua«, 

 and it may be asked if they are not an effete mate- 

 rial, which, not being contained in projier organs, 

 is with these Helminthes thus subcutaueously 

 deposited. 



« This organ, to which I first called the attention 

 in the dissertation of Bagge (I)e evolutione S;r<in- 

 gyli auricularis et Ascaridis acuniinatae, 1841, \>. 

 13), is comi>osed of two canals whicti run back- 

 wards in Strongylus auricularis, Ascaris brevi- 

 caudata, and acuminata {Basse, loc. cit. fig. 30, 

 A. B.) ; and in Ascaris dm-ti/tiiris, -auiI pauri- 

 para, mihi (from the iiiir^tiiin.i ■fisludii smeca), 

 of two anterior and p i-^hiiMi- (finals, the cununoii 

 opening of which is near llie middle of the body. 



