110 G. H. PARKER 



surface make their way only slowly through the wall to the 

 receptive ectoderm, an operation which can be demonstrated in 

 the case of acetic acid. 



7. If there is a nervous layer in the entoderm of the tentacles 

 of Condylactis, it must be extremely simple in structure and 

 function as compared with that in the ectoderm. 



8. The tentacles of Condylactis through their reactions ex- 

 hibit marked polarity, ciliary and neuromuscular. The neuro- 

 muscular polarity disappears on narcotisation with chloretone. 

 It is probably dependent upon the direction taken by the nerve 

 fibrils which emerge from the sense cells. Where this direction 

 has been determined, it is predominantly toward the proximal 

 end of the tentacle. 



9. The actinian tentacle, in contradistinction to such append- 

 ages as those of the arthropods or the vertebrates, contains a 

 complete neuromuscular mechanism by which its responses can 

 be carried out quite independently of the rest of the polyp. 



BIBLIOGRAPHY 



CHESTER, W. M. 1912 Wound closure and polarity in the tentacles of Metrid- 

 ium marginatum. Jour. Exp. Zool., vol. 13, pp. 451-470. 



CROSELJ, P. 1909 Untersuchungen ueber das Nervensystem der Aktinien. 

 Arb. Zool. Inst., Wien, Tom. 17, pp. 269-308. 



HEIDER, A. R. v. 1879 Cerianthus membranaceus Haime. Sitzb. K. Akad. 

 Wissensch., Wien, math.-nat. Cl., Bd. 79, Abt. 1, pp. 204-254. 



JORDAN, H. 1907 Die Verdauung bei den Aktinien. Arch. ges. Physiol., Bd. 

 116, pp. 617-624. 



PARKER, G. H. 1896 The reactions of Metridium to food and other substances. 

 Bull. Mus. Comp. Zool., vol. 29, pp. 107-119. 



PARKER, G. H., AND TITUS, E. G. 1916 The structure of Metridium (Actinoloba) 

 marginatum Milne-Edwards with special reference to its neuromuscu- 

 lar mechanism. Jour. Exp. Zool., vol. 21, pp. 433-459. 



RAND, H. W. 1909 Wound reparation and polarity in tentacles of actinians. 

 Jour. Exp. Zool., vol. 7, pp. 189-238. 



1915 Wound closure in actiuian tentacles with reference to the prob- 

 lem of organization. Archiv fur Entwickelungsmechanik, Bd. 41, 

 pp. 159-214. 



UEXKULL, J. v. 1909 Umwelt mid Innenwelt der Tiere. Berlin, Svo, 259 pp. 



WOLFF, M. 1904 Das Nervensystem der polypoiden Hydroza und Scyphozoa . 

 Zeit. allg. Physiol., Bd. 3, pp. 191-281. 



