44 



THE POLYPI. 



^^ 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 

 Campayuilaria, 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. But 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 o^ Actinia are entirely covered by ciliated 

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



3 Quatrefas:es, Ann. d. Sc. Nat. XVIII. 1842, 

 p. 2S0, pi. VIII. fi^. 1, d, d, and fig. 6. 



4 See Kruhn (Miiller's Arch. 1843, p. 176) and 

 Kblliker (Froriep's neue Notizen, 1843, No. 534, p. 

 81). yan Beneden has perceived in the campa- 

 nulate and free individuals of Campanularia ge- 

 latinosa and geniculata, not only eight marginal 

 bodies, each containing a calcareous nucleus, but 

 also four nervous ganglia about the base of the 

 stomach (>lfm. sur les Campauulaires de la c6te 

 d'Ostende, 1843, p. 24-27,pl. II%ni.). I am yet 

 undetermined upon the question whether, as Van 

 Beneden thinks, these bodies have sometimes the 

 f\inction of organs of vision, and sometimes that 

 of organs of hearing. I am also in doubt as to the 

 opinion of Husclike (Lehre von den Eingeweiden 

 und Sinnesorganen, 1844, p. 880), who regards as 

 otolites the calcareous bodies which have been ob- 

 served in the peduncle of Veretillum cynomo- 

 rium. Nordmann (Versuch. einer Monogr. des 

 Tergipes, p. 88) has described as auditory organs 

 the marginal bodies of the free-swimming Campa- 

 nulariae. 



I This cavity which is in the arms of most Polyps 



does not open outwards at the extremity of these 

 organs. I doubt, in fact, if the Actinina are an ex- 

 ception to this. It therefore appears singular that 

 Rymer Jones (A General Outline of the Animal 

 King. p. 41, fig. 13), and Lesson (Duperrey, Voy- 

 age autour du Monde. Zoophytes, p. 82, No. 1, fig. 

 1), e.x'pressly mention and distinctly figure these 

 openings ; the first with an Actinia, the second 

 with an Eumenides. According to Van Beneden 

 (loc. cit. p. 15) the tentacles of Campanularia 

 are without these cavities. But this is contrailict- 

 ed by Loven (lViegmann''s Arch. 1837, Bd. 1, p. 

 252). In Hydra the cavities open distinctly into 

 the stomach, as is probably the case with many other 

 Hydrina. Frey and Leuckart likewise doubt the 

 constant presence of an orifice at the apex of the 

 tentacles of the Actiniae* 



2 Actinia, Hydra, Flustra and Campanularia. 



3 Veretillum, Lobularia, Isis, Gorgonia, and 

 Zoanthus. 



4 Hydra, Flustra, Zoanthus and Veretillum. 



5 Actinia and Caryophylli(f. 



6 Veretillum, Flustra, Eschara, Cristatella 

 and Tubulipora. 



*[§36, note 1.] Subsequent researches have 

 shown that the cavity of the tentacles does open 

 externally through a small papilla. See Dana, 



Structure and Classification of Zoophytes. Phil- 

 1846, p. 32. — Ed. 



