118 



THE HELMINTHES. 



^113. 



CHAPTER VIII. 



OEOANS OF SECRETION. 



§ 113. 



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

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

 the posterior 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 caudale 

 with Distomum, Holostomum, Monostomum, 

 Aapidog aster, and Diplostomum, has formerly 

 been c mipared to an anus by Nardo (Heusin- 

 ger''s ZL'itscli. fiir organische Phys. 1827, I. p. 68), 

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

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

 in Distomum hepaticum, to a particular organ 

 which is ramified lilie a vessel, has properly re- 

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

 the larvae of Trematodes, known as Cercaria, 

 Bucephalus, and Distomum duplicatun^ the 

 base of the tail is thrust into the excretory opening 

 of this organ, and its contents cannot escape until 

 the animal lias lost the tail. 



2 Amphistomum. 



3 Monostomum faba, Distomum cirrigerum, 

 Gasterostomum jimbriatum, and Bucephalus 

 polymorphus. 



4 Distomum chilostomum, clavigerum, lima, 

 maculosum, tereticol/e, variegatum, and many 

 species of Monostomum, — where the two closed 

 ends of the sac often extend to the cephalic ex- 

 tremity. With Distomum appendiculaturn, the 

 two branches of the excretory organ unite directly 

 behind the oral sucker. With Aspidogaster con- 

 chicola, it divides into two canals near the Fora- 

 men caudale, which extend to the anterior ex- 

 tremity. In Amphistomum, two similar canals 

 wind trom the head along each side of the body, to 

 the middle of the posterior back, where they open 

 outwards, after having formed by reunion a pyri- 

 form reservoir. Laurer (De Amphistomo conico. 

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

 in which he has confounded the secretory canals 

 with the nutritive vessels. 



5 Beside Distomum hepaticum, Holostomum 

 urnigerum, the Distoma also with a spinous 

 head, have a widely-ramified excretory organ ; see 

 Mehlis, Isis,1831, p. 182. 



<) With the spinous-headed Distomum militare, 

 and echinatum, this organ is often so reduced in 

 substance, that here and there are perceived only 

 isolated groups of the ramified canals. 



!■ The solidity of these corpuscles may hare 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. 

 lig. 7) has regarded their escape from the body 

 with Distomum annuligerum, as an act of ovi- 

 jjosition. 



Tlie 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 aspect, of the small 

 calcareous subcutaneous bodies of many Taeniae, 

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

 rial, which, not being contained in proper organs, 

 is with these Ileliiunthes thus subcutaneously 

 deposited. 



s This organ, to which I first called the attention 

 in the dissertation of Bagge (De evolutione Stron- 

 gyli auricularis et Ascaridis acuminatae, 1841, p. 

 13), is composed of two canals which run back- 

 wards in Strongylus auricularis, Ascaris brevi- 

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

 A. B.) ; and in Ascaris dactyluris, and pauci- 

 para, mihi (from the intestine of Testudo graeca), 

 of two anterior and posterior canals, the common 

 opening of which is near the middle of the body. 



