1876.] and Development 0/ Antedon rosaceus. 453 



upheld by Greef (loc. cit.), who says that it gives off: vessels to the cirrhi, 

 and regards what I have described as a circular conmiissure (analogous 

 to the " circle of Willis ") as a closed blood- vascular system in connexion 

 with this, although he admits that the axial cords of the arms, which 

 are derived from this ring, are solid. The careful and repeated investi- 

 gations I have made on this point, however, have fully satisfied me that 

 my previous statement was correct. There is no passage whatever out of 

 the chambers into the axial cords either of the cirrhi or the rays ; and in 

 the pedunculate Crinoids, as in the early Pentacrinoid stage of Antedon, 

 there is no ventricular dilatation, the solid radial cords directly arising 

 from the axis. 



Experiment 1.— -Taking up a large and vigorous specimen of Antedon, 

 I turned the entire visceral mass out of the calyx, leaving behind it, 

 therefore, as the centrum of the animal, only the calcareous segments of 

 the calyx with their muscles and ligaments, the centro-dorsal basin with 

 its cirrhi, and the five-chambered organ contained in the cavity of that 

 basin. On replacing the animal in the water, it executed the usual sivim- 

 ming movement as perfectly as the entire animal had previously done. 



Experiment 2. — I removed from a second specimen, which I took out 

 of the water in the act of swimming, the entire centro-dorsal basin, with 

 its contents and appendages, leaving every other part as it was. On re- 

 placing the animal in the water, all the arms ivere rigidly straightened out, 

 apparently by the action of the elastic ligaments, which the muscles were 

 powerless to antagonize. 



This second experiment, then, not only confirmed my previous belief 

 that the source of the perfect coordination of the swimming movements 

 lies in a Nervous centre, but seemed to establish beyond doubt that the 

 quinquelocular organ is the instrument of that coordination — the centre 

 of a Nervous system, whose peripheral portion consists of the axial cords 

 of the rays, arms, and pinnules. On the other hand, the first experiment, 

 taken in connexion with the second, clearly shows that nothing contained 

 in the Visceral mass is essential to the perfect coordination of the swim- 

 ming movements. And since it is clearly in the oral ring that we should 

 expect to find the centre of any nervous system lying immediately be- 

 neath the tentacular furrow, it seems to me fair to conclude that the 

 supposed " nerve " of Ludwig, if a nerve at all, has no immediate 

 relation to those movements. 



Experiment 3. — I divided, in another lively specimen of Antedon, the 

 soft parts of one of the arms down to the calcareous segment, thereby 

 cutting through the "nerve" of Ludwig. This ought, on his supposition, 

 to paralyze the arm so treated, or at any rate to destroy the consen- 

 taneousness between its movements and those of the other arms. But 

 on replacing the specimen in water, all the arms ivorked as usual, without 

 the slightest disturbance of regularity. 



