^^ 105, 106. THE HELMINTHES. Ill 



CHAPTER IV, 



ORGANS OF SENSE. 



§ 105. 



The sense of touch is probably the only one well developed with the Hel- 

 minthes. The granulations, warts, papillae, filaments, and retractile lobes, 

 found upon the head of some species,^^* are, without doubt, the organs of 

 this function. Tlie red and black points upon the back of many, both adults 

 and larvas, and which have been regarded by some naturalists as organs of 

 vision, appear to be only pigmentary spots ; for they contain nothing like a 

 light-refracting body.^'' 



CHAPTER V. 



DIGESTIVE APPARATUS. 



§ 106. 



The digestive organs with the Helminthes have a variable degree of 

 development in the different orders. 



In the Cystici, Cestodes, and Acanthocephali, neither mouth nor alimentary 

 canal is perceived. In the first two orders, there is, however, a system of 

 vessels which may be regarded as a digestive apparatus ; but these are 

 designed for circulation, rather than for digestion, since their walls are com- 

 plete throughout and have no openings, as has erroneously been supposed, 

 which communicate with the suckers of the head ; and thSir contained nutri- 

 tive material is received by them through the skin in an endosmotic manner.'^* 



1 These tactile granulations are found witli many zur. Infusorienkunde, p. 29, Taf. I.) has described 

 species of Ascaris, as, for instance, in Ascaris in Cercaria ephemera ; I have seen only two 

 «scwtoia, between the large oral collars ; in PA i/sa- upon the back of many cercarian lai-vie. Of this 

 loptera alata, they surround the oral extremity of same nature are the two red dots of Sco/ex poly- 

 the body as a single row ; but they form a double morphus {Müller, Zool. Danica. Tab. LVIII. fig. 

 one in Ascaris trunculata. With Distomum 16, 17), as also the brown ones upon the neck of 

 laureatiim, and nodulosum, they are found upon Oyrodactylus auriculatus {Nordmann Microgr. 

 the borders of the oral sucker. Viiih Holostomum Beitr. lift. I. ]). lOS, Taf. X. fig. 4). Finally may 

 excavatum. emd podoinorpfium, there are two re- be mentioned Amphistomum subclavatum. which 

 tractile lobules protruding from the sides of the has two large oval black dots upon its neck. These 

 mouth ; and in Holostomum alatum, these have pigment-cells are physiologically, without doubt, 

 antenna-like filaments; see NitzscWs figures of simply colored spots, which in Polystomum inte- 

 Holostomum, in Er sch and Graber's Encyclop. g-errrm um are highly developed, forming a widely- 

 Ill, p. 399, IX. spread subcutaneous net-work. Sometimes, and 



2 These dark pigment-dots upon the infusori- especially in the various Cercariae, and in many in- 

 form embryos of many Trematodes when they es- dividuals of Amphistomt/m subclairitiim, these 

 cape from the egg, and of which there is only one dots have a very effaced aspect ; this is probably 

 upon the neck of /)«s<omMTOno(Z«7osH7«, anAfiians, due to a dissolution of the walls of the cells, — the 

 and two upon Monosto?num mutabile, have been pigment-granules being then scattered through the 

 taken for eyes by Nordmann (Microgr. Beitr. Hft. skin. 



2, p. 139), and formerly by myself also (fVieg- 1 It has already been observed that the four 



mann''« Arch. 1835, I. p. 69, Taf. I. fig. 3, 4, 5). suckers of Taenia, regarded by Nitzsck as oral 



Three of these dots have been observed upon a orifices, are imperforate at their bottom. Owen 



.larva of a Monostomum which NiUsch (Beitr. (Cyclop. Anat. &c. II. p. 131) has fallen inte a 



