

ORGANS OF DIGESTION. 333 



of the animal, having a flat foliaceous tapering form, are dis- 

 posed like imbricated scales, and are perforated like the 

 abdominal feet. Numerous long salivary follicles (1 15. d. d.) 

 pour their colourless secretion into the mouth, and near 

 them are placed the two long ramified coloured ovaries (115. 

 e. e.} as in other holothurise. From the dental apparatus, sur- 

 rounded by the muscular parts and integuments of the 

 mouth (115. a. c.), the narrow oesophagus (115./.) leads 

 to a capacious and lengthened stomach (115. g.) with nu- 

 merous vessels (115. h.) extending from its parietes along 

 the reticulate mesentery. The intestinal canal (115. f. g. i.) 

 which in some species is more than ten times the length 

 of the whole body, is here only about twice that length, 

 and was found turgid with sand. The rectum 115. k.) with 

 strong parietes, terminates at the upper part of a long 

 cloaca (115. /.) which is supported by numerous lateral 

 bands (115. m. m.) and presents on its two sides the wide 

 orifices (115. r.) of the long ramified arborescent branchiae 

 (115. p. p. o. o.) which ascend as high as the mouth. 

 The anal opening (115. n.) of the cloaca, and the orifices 

 (115. r.) of the two gills, are here so wide and so constantly 

 open, that Crustacea more than a quarter of an inch in 

 diameter, were found living and residing in these passages, 

 and this active cloaca was found to retain its high irrita- 

 bility after the animal had been cut to pieces. The dental 

 organs, so powerful and complicated in the cidaris and 

 echinus, and so variable in their extent of development in 

 the holothur'uB and fistularia, have lost their calcareous 

 matter in the priapulus, and are wanting in the long ver- 

 miform sipunculi which present a lengthened retractile tu- 

 berculated head, a wide funnel-shaped oesophagus, and a con- 

 voluted alimentary canal many times the length of the body, 

 destitute of gastric dilatation, furnished with a few biliary 

 follicles, and returning from behind to open externally near 

 the mouth. Thus the digestive cavity, from the condition 

 of a simple monostome sac, filling the whole abdomen, in 

 the lower stellated forms of these animals, has gradually 

 acquired the form of an elongated tubular narrow canal, open 

 at both ends, and furnished with biliary and salivary follicles, 

 in the helminthoid echinoderma, as in many helminthoid 

 articulata. 



