640 A. MILNES MARSHALL. 



These results are in complete accordance with the views so 

 steadfastly advocated for many years past by the Carpenters, 

 and recently adopted by Perrier, while, on the other hand, they 

 are in direct opposition to the tenets of the German school.^ 



IV. Morphological Considerations. 



Certain points of very considerable morphological interest 

 arise in connection with the results detailed above, and I 

 propose in this concluding section to notice briefly a few of the 

 more important of these. 



In the first place the morphological difficulty arising from the 

 possession byAntedon of an antambulacral in addition to the typical 

 ambulacral nervous system of Echinoderms must be considered. 

 This objection has been strongly urged by Ludwig, and consti- 

 tutes indeed the real ground of his dissent from Dr. Carpenter's 

 views ; and it must be admitted that the presence of a compli- 

 cated nervous system in Crinoids, which is apparently altogether 

 unrepresented in other Echinoderms, is a feature which a 

 morphologist might well shrink from accepting until the 

 fullest proof was forthcoming. This proof I have attempted 

 to supply in the preceding section ; the morphological puzzle 

 however, still remains to be considered. 



Tiedemann^ was the first to describe the ambulacral nervous 

 system of Echinoderms, and since his time the five radial 

 bands with their connecting circumoral commissure have been 

 universally accepted as constituting the typical Echinoderm 

 nervous system. This nervous system, as was pointed out 

 by Tiedemann, is diffierently situated in the different groups : 



1 Since this paper was written Dr. Jickeli, of Jena, has published an account 

 of experiments made on the nervous system of Antedon, which led him to 

 strongly uphold the correctness of Dr. Carpenter's views. Many of Jickeli's 

 experiments are identical with the ones described above, and his paper, 

 (' Zoologischer Anzeiger,' 23rd June, 1884), although at present incomplete, 

 contains much valuable information. 



2 Tiedemann, ' Beobachtungen ueber das Nervensystem und die sensiblen 

 Erscheinungen der Seesterne ;' Meckel's, ' Archiv fiir Physiologie,' Bd. i, 

 1815 : and ' Anatomic des Rohrenholothuries, des Seesterns und Steineigels,' 

 Laudshut, 1816. 



