44 THE POLYPI. *§>§ 35, 36. 



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

 whole. *^' 



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

 Campanvlaria, 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 of Actinia are entirely covered by ciliated 

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



3 Quatrefages, Ann. d. Sc. Nat. XVIII. 1842, does not open outwards at the extremity of these 



p. 280, pi. VIII. fig. 1, d, d, and fig. 6. organs. I doubt, in fact, if the Actiniiia are an ex- 



i See Krohn (MuUer''s Arch. 1843, p. 176) and ception to this. It therefore appears singular that 



.ffoHiyter (Frorie/7's neue Notizen, 1843, No. 534, p. Rymer Jones (A. General Outline of the Animal 



81). Van Beneden has perceived in the campa- King. p. 41, fig. 13), and Lesson (Duperrei/, Voy- 



nulate and free individuals of Campanularia 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 



bodies, each containing a calcareous nucleus, but openings ; the first with an Actinia, the second 



also four nervous ganglia about the base of the with an Eumenides. According to f^an Beneden 



stomach (Mfm. sur les Campanulaires de la cdte (loc. cit. p. 15) the tentacles of Campanularia 



d'Ostende, 1843, p. 24-27, pi. II. III.). I am yet are without these cavities. But this is contradict- 



undetermined upon the question whether, as Van ed by Lov^n {Wiegmann^s Arch. 1837, Bd. 1, p. 



Beneden thinks, these bodies have sometimes the 252). In Hydra the cavities open distinctly into 



function of organs of vision, and sometimes that the stomach, as is probably the case with many other 



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



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



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



otolites the calcareous bodies which have been ob- 1 Actinia, Hydra, Flustra &ni Campanularia. 



served in the peduncle of Veretillum cynomo- 3 Veretillum, Lobularia, Isis, Gorgonia, and 



rium. Nordmunn (Versuch. einer Monogr. des Zoanthus. 



Tergipes, p. 88) has described as auditory organs < Hydra, Flustra, Zoanthus and Veretillum. 



the marginal bodies of the free-swimming Campa- 5 Actinia and Caryophyllia. 



nulariae. ^ Veretillum, Flustra, Eschara, Cristatella 



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



*t§36, note 1.] Subsequent researches have Structure and Classification of Zoophytes. PhU. 

 shown that the cavity of the tentacles does open 1346, p. 32. — Ed. 

 externally through a small papilla. See Dana^ 



