$$ 105, 106. THE HELMINTHES. 111 
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. 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 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 their contained nutri- 
tive material is received by them through the skin in an endosmotic manner.” 
1 These tactile granulations are found with many 
species of Ascaris, as, for instance, in Ascaris 
osculata, between the large oral collars ; in Physa- 
optera alata, they surround the oral extremity of 
the body as a single row ; but they form a double 
one in Ascaris trunculata. With Distomum 
daureatum, and nodulosum, they are found upon 
the borders of the oral sucker. With Holostomum 
exrcavatum, and podomorphum, there are two re- 
tractile lobules protruding from the sides of the 
mouth; and in Holostomum alatum, these have 
antenna-like filaments ; see Nitzsch’s figures of 
Holostomum, in Ersch and Gruber’s Encyclop. 
IIL. p. 399, IX. : 
2 These dark pigment-dots upon the infusori- 
form embryos of many Trematodes when they es- 
cape from the egg, and of which there is only one 
upon the neck of Distomum nodulosum, and hians, 
and two upon Monostomum mutabile, have been 
taken for eyes by Nordmann (Microgr. Beitr. Hft. 
2; p. 189), and formerly by myself also (Wiex- 
mann’s h. 1835, I. p. 69, Taf. I. fig. 3, 4, 5). 
Three of these dots have been observed upon a 
darva of a Monostomum which Nitzsch (Beitr. 
zur. Infusorienkunde, p. 29, Taf. I.) has deseribed 
in Cercaria ephemera; I have seen only two 
upon the back of many cercarian larve. Of this 
same nature are the two red dots of Scolex poly- 
morphus (Muller, Zool. Danica. Tab. LVITI. fig. 
16, 17), as also the brown ones upon the neck of 
Gyrodactylus auriculatus (Nordmann Microgr. 
Beitr. Hft. I. p. 108, Taf. X. fig. 4). Finally may 
be mentioned Amphistomum subclavatum, which 
has two large oval black dots upon its neck. These 
pigment-cells are physiologically, without doubt, 
simply colored spots, which in Polystomum inte- 
gerrimum are highly developed, forming a widely- 
spread subcutaneous net-work. Sometimes, and 
especially in the various Cercariae, and in many in- 
dividuals of Amphi. subcl , these 
dots have a very effaced aspect; this is probably 
due to a dissolution of the walls of the cells, — the 
pigment-granules being then scattered through the 
Bkin. 
1It bas already been observed that the four 
suckers of Taenia, regarded by Nitzsch as oral 
orifices, are imperforate at their bottom. Owen 
(Cyclop. Anat. &c. II. p. 181) has fallen intea 
