OKUAXS OF DIGESTION. .W.) 



body. The straight and wide intestine of the stronyylus yi- 

 yas appears to be surrounded with short biliary follicles 

 during the greater part of its course through the body. In 

 the highest animals of this class, as the achtheres, ierntea, 

 peniculus, tracheliastes, brachiella and chondracantfyus, which 

 have a more entomoid form, and suck the vital fluids from 

 the delicate exterior parts of the skin of aquatic animals, the 

 mouth is already provided with small lateral unciform mandi- 

 bles, adapted to tear the surface to which the animals are 

 fixed ; and their alimentary canal, wide and short and with a 

 terminal anal aperture passes straight through the body, 

 surrounded by the biliary follicles and by the genetal organs, 

 as in higher articulated classes. 



VII. Rotifer a. In the minute and transparent bodies of 

 the wheel-animalcules we observe the digestive, like the other 

 organic systems, to present the typical forms of the articulat- 

 ed animals. Their large transverse maxillae (Fig. 12.) are 

 moved by a powerful muscular apparatus (Fig. 11. b.) and ap- 

 pear in incessant action while they are surrounded by minuter 

 animalcules. Their carnivorous character is seen alike in the 

 living and mangled contents of their transparent stomach 

 (Fig. 1J. A.), and in the short and straight course of their 

 alimentary canal (Fig. 82. B). The alimentary cavity in 

 some, as the hydatina sent a (Fig. 11 7- A.) passes straight, 

 simple, and uniform from the narrow ossophagus (11 7- A. f.) 

 to its'posterior cloacal termination, without any perceptible 

 lateral coaca or follicles. They pursue their prey by vibrat- 

 ing the anterior circles of cilia (117- A. a.) by the muscular 

 lobes at their base which are attached to ligamentous bands 

 (117. A. b.) The large cerebral ganglion (11 7- A. c.) and 

 the smaller lateral ganglia (117- A. d.) surround the strong 

 muscular pharynx (117- A. e.) which is capable of being 

 protruded and retracted to a great extent and with great ra- 

 pidity. The living animalcules (11 7- A. g.) contained in the 

 stomach are easily perceived, and the whole internal structure, 

 through the hyaline texture of their body, and small glandu- 

 lar sacs (117. A. h.) are seen at the sides of the oesophagus 

 (117. A./.) which appear to send ducts to the muscular 

 pharynx (117- A. e.) embracing the masticating organs. The 

 dorsal vessel (117- A. L) extends along the middle of the 

 back, sending off numerous lateral branches in its course 



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