^ 154. THE ANNELIDES. 165 



With the Hirudinei, the intestinal canal varies very much, especially as 

 to the number and volume of its appended coeca.*-* Its very narrow anal 

 opening is upon the back directly above the pedal sucker. '"> With Nephe- 

 lis, the canal is simple and gradually enlarges from before backwards, but 

 has no coeca. ' 



With Branckiobdella, it is deeply constricted in several places.**^ With 

 Pontobdella, it is simple with its two anterior thirds, but there is a caecum 

 on each side of its remaining portion.''^ This last is also true of its posterior 

 third with Haemopis, Clepsine, and Saiiguisuga}'^'' With this last genus, 

 the other portions of the canal are divided by ten or eleven constrictions 

 into as many parts which send off on each side short caeca ; '''^ while that 

 of Clepsine has on each side five or six coeca, all of which may be rami- 

 fied. There is a kind of valve directly behind the last two caeca, and so 

 the part of the intestinal canal in front of this may be regarded as a stom- 

 ach and a small intestine, while the remaining portion behind it, represents 

 the rectum. ^'^^ 



With the Abranchiati, the intestinal canal is short, and its oesophagus 

 which is usually narrow passes into a muscular pharynx, which leads into 

 a stomachal dilatation. Upon these parts follow the remaining portions of 

 the intestine which are separated from each other by the transverse septa 

 of the body and often resemble the stomach. With a few species only, tho 

 stomach is remarkable for its thick, muscular walls. '^' 



With some of the Capitibranchiati, the digestive canal arises directly 

 behind the oesophagus and has bulging portions like those of the colon. f^"* 

 assuming, posteriorly, sometimes a spiral form.*"^ With others, the oesoph- 

 agus is continuous directly into the intestinal canal, which, free and un- 

 attached by diaphragmatic septa, makes many turns in the cavity of the 

 body, and by constrictions is divided into a stomach, small intestine, and 

 rectuip.^^' 



With many Dorsibranchiati, the intestine follows directly upon the 

 oesophagus, and is either straight and divided by constrictions, ^^'^^ or assumes 

 a spiral form '"' or is without constrictions and irregularly tortuous. ^'^ 

 With others, the portion of intestinal canal between the pharynx and in- 

 forms with the buccal orifice, a cavity distinct from 10 Terebella, and Sabella ; see Grube, Zur 

 tliat of the abdomen, and its anus has a kind of Anat. d. Kiemenwürmer, p. 20, 27, Taf. II. fig. 

 sphincter. But this is certainly an erroneous view 12, and Milne Edwards, Ann. d. Sc. Nat. X. 

 of the organization of these worms : the contents 1838, PI. X. XI. 

 of the cavity are suSicient alone to confute it. 11 Sabella ; see Cams and Otto, Erläuterungs» 



2 Moquin-Tandon, loc. cit. PI. I.-IV. taf. Hft. IV. Taf. III. fig. 4, 6, and fVagner, Icon. 



3 Witli Piscicola, e.xceptionally, the anus is up- zoot. Tab. XXVII. fig. 21. 



on the ventral surface of the last segment of tlie 12 Amphitrite, and Siphnnostomum. With the 



body ; see Leo, in MuUer^s Arch. 1835, p. 420. first, the stomach is long, spiral, and divided into 



4 Henle, Miiller^s Arch. 1835, Taf. XIV. fig. 1. an ascending and a descending portion ; see Rath- 



5 fVagncr, Isis, 1834, p. 130, Taf. I. fig. 1, 2. ki, Danzig. Schrift, loc. cit. p. 64, 86, Taf. V. VI. 



6 Brandt and Ratzeburg, Med. Zool. II. p. 246, 13 Amphinome, Arenicola, Eunice, and Neph' 

 Taf. .X.XIX. B. fig. 12. tys ; see Stamiius, Isis, 1831, Taf. VI. fig. 10 : 



7 Ibid. Taf. XXIX. A. fig. 19, 20, 55. Milne Edwards, Ann. d. Sc. Nat. X. 1838, PI. 



8 With Clepsine margitiuta, this rectum has XII. XIII. ; Grube, Zur Anat. d. Kiemenwürmer, 

 coecal appendages also ; see F. Müller, in fVieg- Taf. I. 



mann's Arch. 1844, I. p. 371, Taf. X. fig. 14.* U According to Grube (Ibid. p. 34), the intes- 



Ö 'With Lu7nbrici(S, the stomach is very muscu- tine of Cirratulus is spiral like that of Sabella. 



lar ; see Morren, loc. cit. Tab. XI.-XIV. This is 15 Ammotrypane (according to Grube, sea 



also true of Nais proboscidea, but not with Lum- Rathki, Nov. Act. Acad. Nat. Cur. XX. p. 197, 



briculus, and Enchitraeus. Tab. X. fig. 13). 



* [ § 154, note 8.] For many special details Clepsine, Nephelis), see Leydig, loc. cit. p. 110, 

 illustrating as well the histology as the anatomy of Taf. VIII. IX. fig. 24-37. — Ed. 

 the intestinal canal of the Hirudinei {Piscicola, 



