44. THE POLYPI. ^"^i 35, 36. 



it a cornea, a crystalline lens and a red pigment layer surrounding the 

 whole/'^ 



Furthermore, there are upon the border of the disc of the campanulate 

 Campamduria, colorless corpuscles, containing a calcareous nucleus, which 

 is transparent as a crystal and soluble in acid. 



These organs should probably be regarded as the most simple form of 

 the auditory organs, for they have only a simple vestibule with its single 

 otolite.'-*'' 



CHAPTER V. 



DIGESTIVE APPARATUS. 



§35. 



The digestive apparatus of Polyps is formed after two different types. 

 With the Anthozoa it consists of a mouth and a simple stomachal sac with- 

 out an anus. Bat with the Bryozoa, there is a mouth and anus, and a 

 digestive canal which may be divided into the sections of oesophagus, 

 stomach, small intestine and rectum. 



§36. 



The mouth of Polyps is usually surrounded by a circle of long, very 

 ■contractile tentacles or arms. These tentacles are tubular, and connect with 

 the cavity of the body.'"' They are simple,^-' or pennate/'^' and may be dis- 

 posed around the mouth in a single^^' or a multiple'"'' circle ; they are also 

 frequently covered with cilia.'®' 



Thus, the cylindrical tentacles of Actwia are entirely covered by ciliated 

 epithelium. With the Bryozoa, on the contrary, the slightly-tiattened ten- 

 's Quatrefa.ffes, Ann. d. Sc. Nat. XVIII. 1842, does not open outwards at the extremity of these 

 p 280, pi. Vlii. tig. 1, (1, d, and fig. 6. organs. I doubt, in fact, if the Actiuina are an ex- 



■1 See A>o/(H (i>/««cc's Arch. 1843, p. 176) and ct-ption to this. It therefore appears singul;u- that 

 A'd'/iAe/- (Fror(fi;)'s neue Notizen, 1843, No. 534, p. Rymer Jones {K General Outline of the Animal 

 81). Vail Bene.den has perceived in the canipa- King. p. 41, fig. 13), and Lesson (Dnperreij, Voy- 

 nulate and free individuals of CampamUaria ge- age autour du Monde. Zoophytes, p. 82, No. 1, fig. 

 latinosa and geniculata, not only eight marginal 1), expressly mention and distinctly figure these 

 J)udies, each containing a calcareous nucleus, but openings; the first with an Actinia, the second 

 also four nervous ganglia about the base of the with im Enmenides. According to Fan Ben edrn 

 •stomach (M^m. sur les Campanulaires de la cote (loc. cit. p. 15) the tentacles of Campanularia 

 <i'<)stenile, 1843, p. 24-27, pi. II. III.). I am yet are without the.se cavities. But this is contradict- 

 undetermined upon the question whether, as Van ed by Lovhi (It^ifK' mannas Arch. 1S:',7, lid. 1, p. 

 ßeueden thinks, these bodies have sometimes the 252). In f/ydr« thf cavitii'S ojien distinctly into 

 function of organs of vision, and sometimes that the stomach, as is probably tlie c;isi- witli many other 

 of organs of hearing. I am also in doubt as to the Hydrina. Frey and LeucAarMikewise doubt the 

 opinion of Huschke (Lehre von den Eingeweiden constant presence of an orifice at the apex of the 

 mud Sinnesorganen, 1844, p. 880), who regards as tentacles of the Actiniae.* 



lOtriRtes the calcareous bodies which have been ob- 2 Actinia-, Hydra, Flustra and Campanularia. 

 «•Tved in the peduncle of yeretillum cynomo- 3 Veretillam, LoOularia, Isis, Gorgonia, and 

 rium. JSordmann (Versuch, einer Monogr. des Zoanthus. 



Tergipe«, p. 88) has described as auditory organs i Hydra, Flustra, Zoanthus and Veretillum, 

 the marginal bodies of the free-swimming Campa- C Actinia and Caryophyllia. 

 nulariac. •> yerrtilhirn, Flustra, Eschara, Cristalclla 



1 This cavity which is in the arms of most Polyps and Tubulipora. 



*l§36, note 1.] Subsequent researches have Structure and Classillcation of Zoophytes. Phil, 

 «hown that the cavity of the tentacles does open 1846, p. 32. — Ed. 

 exteruully through a small papilla. See Dana, 



