408 THE VOYAGE OF H.M.S. CHALLENGEE. 



a summary of the researches of his predecessors, though he states that he has himself 

 made some observations on Antedon rosacea at the Zoological Station at Trieste. It was 

 perhaps not to be expected that he should have done otherwise than propagate the 

 orthodox German view respecting the nervous system. But the account which he gives 

 of the position in 1883 of the doctrine that the axial cords are nerves, is an extremely 

 inadequate one. He states (p. 283) that it has been proved to be incorrect by Greeff; 

 while a few pages fui'ther on {p. 290) he says that attempts have been made to support 

 it by the supposition {Annahme) that fine branches proceed from the axial cords to the 

 muscles and arm-segments—" Ludwig und Greeff wiesen jedoch das Unzuliingliche und 

 Unrichtige der von Carpenter angefiihrten Argumente nach." He then refers to the 

 experiments performed by Dr. Carpenter, and leaves the question for further investiga- 

 tion. 



Now, in the first place, the only comment which Greeff has made upon the doctrine 

 that the axial cords are nerves has been a simple denial of its truth, without any attempt 

 to discuss the subject at all ; ^ and yet this denial is referred to by Weinberg as a proof 

 of the doctrine being incorrect ! 



Ludwig, on the other hand, admits that the experimental evidence seems to afford 

 very considerable support to Dr. Carpenter's views ; " but he declines to accept them on 

 account of the morphological difficulties which they involve. He has been unable to find 

 the muscular branches from the axial cords which have been described by Dr. Carpenter 

 and myself, and more recently by Perrier, Marshall, and Jickeli. But this does not 

 justify Weinberg in stating that Ludwig has proved the arguments advanced by Dr. 

 Carpenter and myself to be insufficient and incorrect ; nor that the existence of these 

 branches is merely a supposition. The fact that they w^ere overlooked, not only by 

 Teuscher and Greeff, but also by Ludwig and Weinberg, even after I had specially 

 called attention to them, is no proof of their non-existence. Two figures of arm- 

 sections, showing these branches, together with a further discussion of the whole 

 question, were published in my paper '^ On the Minute Anatomy of the Brachiate 

 Echinoderms, which appeared two j^ears before Weinberg ■^Tote his resume, but is not 

 referred to by him at all. 



Another point of consideralile interest in its bearings on this question is left entii-ely 

 unnoticed by Weinberg, though it was fully explained in a paper * which he quotes, and 

 it was illustrated by a diagram which also shows the branches of the axial cords ; although, 

 according to Weinberg, the existence of these branches is a mere supposition. I refer to 

 the frequent absence of the ambulacral nerve on more or fewer of the arms of Actino- 

 metra. Weinberg admits its absence on the oral pinnules of Antedon, for this was 



' TJeljcr <len Ban der Crinoideen, Sit::ungsb. d. Gesellsch. z. Beford. d. nesammt. Naturiciss. zu Marburg, Nro. 1. 

 1876, pp. 21, 22. 



- Crinoideen, loc. cit., p. .3.3.i. s Quart. Joum. Micr. Scl, 1881, vol. xxi., N. S., pp. 188-192. 



* Remarks on the Anatomy of the Arms of the Crinoids, part ii., Journ. Anat. and Phys., vol. xi., 1876, pp. 90-93. 



