REPORT ON THE CRINOIDEA. 409 



discovered by Ludwig, whose observations he could not very well overlook. But he does 

 not attempt to discuss the bearings of this fact on Ludwig's doctrine that the axial cords 

 are the only nerves in the arm of a Crinoid. He likewise describes the regular alternat- 

 ing movements of the arms of a swimming Comatula, and the muscles by which these 

 movements are effected ; and he leaves it to be inferred that these muscles are under the 

 control of the only nervous system of which he admits the existence, although experi- 

 ments have clearly j)roved that this is not the case ; while Ludwig has admitted that he 

 could trace no branches proceeding to the muscles from the ambulacra! nerve. As to 

 this last point, however, Weinberg is altogether silent. 



Until this present year no German morphologist, with the exception of Weinberg, 

 had published any observations upon the Crinoids since the appearance of Ludwig's 

 important work in 1877 ; and the authors of zoological text-books published in Germany 

 have confined themselves with remarkable unanimity to reproducing Ludwig's asser- 

 tions that the nervous system of a Crinoid is essentially similar to that of an Asterid, 

 and is limited to the fibrillar bands beneath the ambulacra. Dr. Carpenter's views, if 

 mentioned at all, which was rare, were regarded as untenable from their being altogether 

 at variance with the established scheme of Echinoderm morphology. Claus, for example, 

 describes the arrangement of the axial cords in the calyx in some detail, but says not a 

 word about their functions ; w^hile their presence is not even mentioned by Gegenbaur. 

 According to these writers, therefore, the nervous system of a complex and highly 

 specialised type like Pentacriniis is exclusively represented by the subepithelial bands of 

 the ambulacra and the oral ring which unites them beneath the peristome (PI. LXIL, n,nr). 

 The extreme insignificance of these structures in comparison with the rest of the organism 

 cannot fail to strike any one who examines the sections of the ambulacra represented on 

 PI. LVIL; and yet, according to the orthodox German morphology, they are the only 

 nerves which a Crinoid possesses. 



The theory that the axial cords are nerves has recently been restated by Di*. 

 Carpenter,' wdth the additional support of a quantity of new facts which had been 

 discovered since he last wrote on the subject, more than eight years ago. He concluded 

 by saying, " those who refuse to accept them (my views) are bound, I think, either to 

 disprove the facts, or to show that my deductions from them are unsound." 



Within a very short time after the presentation of this communication to the Eo}'al 

 Society, two papers were published on the nervous system of the Crinoids, in which 

 Dr. Carpenter's theory was unreservedly adopted and strengthened by a large body of 

 additional evidence. 



The second of these, by Professor A. Milnes Marshall,^ will be best considered first. 

 After a short historical sketch of the subject, he describes an elaborate series of experi- 



1 On the Nervous System of the Crinoidea, Proc. Roy. Soc. Lond., vol. xxxvii., 1884, pp. 67-76. 



^ On the Nervous System of Antedon rosaceus, Quart. Journ. Micr. Sci., vol. xxiv., N. S., 1884, pp. 507-548, iil. xxsv. 



(ZOOL. CHALL. EXP. PART XXXII. — 1884.) li 52 



