^'^ 105, 106. THE HELMINTHES. Ill 



CHAPTER IV, 



ORGANS OF SENSE. 



§ 105. 



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

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

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

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

 and larvae, 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 whicli 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 their contained nutri- 

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



• These tactile granulatinns are found witli many zur. Infusorienkunde, p. 29, Taf. I.) has dcscrihod 

 species of Axcaris, as, fov instance, in Ascaris in Cercaria ephemera ; I have seen only tvro 

 oscM/ain, between the large oral collars ; in PA (/sa- upon the back of many'cercarian larvas. Of this 

 loptera alata, they surround the oral extremity of same nature are the two red dots of Scolex pohj- 

 the body as a single row ; but they form a double morphits (Midler, Zool. Danica. Tab. LVIII. fig. 

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

 iaureatum, 'dnd nodulosiim, ihey are fimoA upon Qyrodactiilns aiiricnlatrta (NordTnann Microgr. 

 the borders of the oral suclccr. 'With Ilolostomum Eeitr. Hft. I. p. lOS, Taf. X. fig. 4). Finally uiny 

 excavatiim, and podomorp/nim, there are two re- be mentioned AmphistorQvm /iubr/nrrUii?n. which 

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

 mouth ; and in Holostomum a/atum, these have pigment-cells are physiologically, without doubt, 

 antenn.a-like filaments ; see Nitzstch^t figures of simply col ired spots, which in Polystomim intr- 

 Holoslomum, in Ersch and Gruier's Encyclop. g'erriTOffjn. are highly developed, forming a widely- 

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



'-' Tliese dark pigment-dots upon the infusori- especially in the various Cercarmw, and in many in- 

 form embryos of many Trematodes when they es- dividuals of Amphifstomnm siibc/avntum, these 

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

 upon the neck ofJii/itomHm. nodulnsum, and liians, due to a dissolution of the walls of the cells, — tlie 

 and two upon Monostomum mntahile, have been pigment-granules being then scattered through the 

 taken for eyes by Nordmami (.Microgr. Beitr. lift. skin. 



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



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



Three of these dots have been observed upon a oi-ifices, are imperforate at their bottom. Oiuen 



larva of a Monostomum wliich Nitzsch (Beitr. (Cyclop. Anat. &c. II. p. 131) has fallen i: t ■ 



