ZOOLOGY AND BOTANY. MICROSCOPY. ETC. 7G1 



and Lave no iufluence on the chemical character of the surface of tlie 

 rocks, aud they cannot therefore be supposed to have any connection 

 with the origin of the Echinus holes. 



Saccular Diverticula of Asteroidea.* — Dr. A. B. Griffiths and 

 Mr. A. Johnstone find that the saccular diverticula are pancreatic iu 

 function ; the same tests were applied as to Tegenaria.'f 



New OpMurids.t — Mr. J. E. Ives describes a new genus of Ophiurids, 

 which he calls OpMoncus (O. firanulosus sp. n.) ; it is the only genus, 

 except OpMura, that has the genital slit divided; but ib differs in having 

 the inner opening larger and not smaller than the outer one. In general 

 characters and in structure of its arm-bones the new genus seems to be 

 nearest to Ophiozona. 



Coelenterata. 



Chun's CcBleiiterata.§ — Prof. C. Chun has commenced a new edition 

 of such of Broun's Klassen u. Ordnungen as dealt with the Coelenterata. 

 The first part deals only with the history of the group. 



Occasional Presence of a Mouth and Anus in Actinozoa.|| —Mr. 

 H. V. Wilson calls attention to the occasional occurrence of actinians or 

 curals in which there are permanently separate openings into the gastric 

 chamber. If the theories of Sedgwick and E. B. Wilson are correct, this 

 is precisely the variation which must have occurred in the ancestral 

 radiate, and to which bilateral animals owe their existence. Among 

 many examples of the large actinian which is called Cereactis hahamensis, 

 one had the free lips of the oesophagus grown together along the 

 sagittal axis, except where the sagittal furrows opened into the gastric 

 chamber. Here there were two small circular openings. The concres- 

 cence was an actual and perfect union of tissue, and the animal was an 

 adult of normal size, and thoroughly healthy. The union of the lips 

 must, however, have affected its ftedinpr, for it must have made it 

 impossible fur the creature to eat small gastropods, such as are often 

 found in the gastric chamber of these anemones. A similar variation 

 was observed in a single swimming larva of the ce>ral Manicina areolata. 



Arrangement of Tentacles in Cerianthus. H — Dr. P. Fischer points 

 out that the view that the tentacles of Cerianthus memhranaceus vary in 

 number, but are always paired, is incorrect, for there is always an odd 

 number of them ; this is due to the presence of an unpaired tentacle, 

 which is constantly found near one of the angles of the mouth, and 

 serves to determine the ventral side of the animal. He finds that the 

 marginal tentacles of the first cycle correspond to the buccal tentacles 

 of the second; that the marginal tentacles <f the second correspond to 

 the buccal tentacles of the third, and that the marginal tentacles of the 

 third cycle correspond alternately to the buccal tentacles of the first and 

 third cycles. 



The bilateral symmetry of Cerianthus is demonstrated by the 

 arrangement of the buccal tentacles, while, on the contrary, the marginal 

 tentacles generally indicate a radial symmetry. On the other hand, the 



* Proc. R. Soc. Ediiib., xv. (18S7-8) pp. 114-5. f See ante, p. 746. 



t Proc. Acad. Nat. Sci. Philar]., 1SS9, pp. 143-6. 



§ Bronn's Klassen u. Ordnuiiiren, ii., 2, Coelenterata (1889), pp. 1-48. 



Il Circ. John Hopk.ns Univ., viii. (1889) pp. 87-8. 



«i Bull. Sof. Zuol. France, xiv. (1889) pp. 24-7. 



