108 THE HELMINTHES. § 104. 



of the last row are only rudimentary. The sheath of the proboscis is very 

 muscular, and terminates behind in a caecum ; it extends across the neck of 

 the animal even into the cavity of the body, and its movements arc aided by 

 some special muscles. In all the species whatever, there are three nmscles 

 which act as retractors of the sheath and neck. Two of these arise as 

 delicate cords at the anterior extremity of the body from both sides of the 

 internal surface of the subcutaneous muscular sac; they traverse thence 

 the cavity of the body obliquely, and are inserted, in Echinorhyyichus acus, 

 angustatus, fi/sifo?'/nis, and proteus, upon the sides of the sheath; but in 

 Echinorhynchus gigas, Jiacmca, polyviorphus, Jiystrix, and struinosus, the 

 insertion is at its inferior extremity. Between these two muscles, and 

 below their points of origin, there is a third, wliich divides from the sub- 

 cutaneous muscular sac ; this is simple, riband-like, and is inserted at the 

 lower extremity of the sheath. In Echi)ior}iynchus polymo7-phus, and ^ro- 

 teus, its form is pyramidal. In Echinorhynchits gigas, and gibbosus, two 

 thin muscles arise from the anterior extremity of the body, and are inserted 

 upon the sides of the sheath ; they serve, probably, for the protrusion of 

 this organ and the neck.*"' 



There are, moreover, upon the different parts of the body of some Hel- 

 minthes, horny hooks and spines, which serve for their creeping about and 

 permanent attachment to objects.*''' 



CHAPTER III, 



NEUVOOS SYSTEM, 



§ 104. 



The apparently quite feebly-developed nervous system of the Helminthes 

 is yet but very incompletely known. 



Our whole knowledge is limited to that of a small obscure ganglion found 

 in some species, which, as it sends off several nerves, may be regarded as 



6 Helmiiithologisls are not yet agreed as to the a sting which projects from the back above the 



niunber and arrangement of the proboscideal mus- oral sucker (and not from the mouth itself, as fVag- 



cles of the Acantliocephali ; see TVi'iZM-A, in £rscA ner has supposed, Isis. 1834, p. 131), and which 



and Gniber's Encyclop. I. 1S18, p. 242 ; Bojanus, serves to open a passage through the parenchyma 



in Isis, 1S21, Taf. III. fig. 34 ; fVestrumb, De of the annuals they infest. An entire group of 



Helmuitlul)us Acanthocephalis 1821, p. 50 ; and Distomu?n, as Distomum ccliinatum, militare, 



Cloquet, Anat. des Vers, intestin. p. 76, PI. VII. uncinatum (Bremser, Icon. Helminth, Tab. X. 



Meklis (Isis 1831, p. 82) has taken the probosoi- fig. 5), which Riidoljilii has designated as Echinos- 



deal sheath for an esophageal organ, and its two tomata, have around their oral sucker an annular 



muscles for vessels. Burow (Echinorliynchi stru- collar, upon which are numerous straight spines 



mosi Anatome, 1836, p. 16, fig. 1, e) has fallen arranged in a circular manner. An armature of 



into a similar error, in regarding these same mus- this kind is found upon a Ccrcuria. Those spines 



cles as iutostinal tuljes. are as easily detached as the hooks of the armed 



^ With many Trematodes, as, for example, with Taeniae. With Spiroptera crassicatida, I have 



Poli/stomum, Octnbothrii/m, (fC. (see Baer, Nov. found on each side of the mouth a douljly-pointed 



Act. Acad. Leop. Carol. ,>CUI. pt. 2, Tab. XXXII. sting pointing backwards, and behind this two 



fig. 7, f. and Mayer, Beitrage, &c., Taf. III. fig. others three-pointed. A still more remarkable 



3, m. m. fig. 8), there are found between the suck- form is seen in the four penniform stings, which 



ers at the posterior extremity, special hooks, and project behind the mouth of Anr ijracanthua 



to which, with Polystomam, I have seen proper pinnatijidus (see Diesin<;, Ann. d. Wi'Mier Mus. 



muscles proceed from the interior of the body. II. Abth. 2, Taf. .XIV. .Will.). These Nematodes 



With certain Ce?-car2ae(larva; of Distomum) one umloubtedly use these instruments fa- piercing the 



can distinctly observe the use which they make of stomachal membranes of the animals they infest. 



