702 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



attempt to right itself or to swim. The arms were then strongly nipped with 

 forceps one by one. Each arm when irritated responded by active movements, but 

 none of the other arms stirred except the other arm of the pair to which the irri- 

 tated arm belonged, which moved sometimes slightly, sometimes actively. 



Experiment 28. A pair of arms was cut off a specimen, the section passing 

 between the radial and the IBr,. After half an hour's interval one of the arms 

 was stimulated, when both arms moved actively. 



Experiment S3. Another specimen was eviscerated and a pair of arms 

 removed, the section passing between the elements of the IBr series. All the soft 

 parts were scraped from the basal portions of the arms, the basal pinnules were 

 cut off, and the axillaries and proximal brachials freely scraped and painted with 

 nitric acid, so that the sole connection between the two arms was through the 

 substance of the axillary. After half an hour one of the arms was sharply nipped ; 

 the irritated arm moved freely, and the other arm slightly, but distinctly. The 

 experiment was repeated with a second specimen, and an interval of three hours 

 allowed between the operation and stimulation of the arm. In this case active and 

 extensive movements of both arms followed on irritation of either one. 



The preceding experiments show that (a) the central capsule and its prolonga- 

 tions, the axial cords and their braches, constitute the main nervous system of 

 Antedon; (b) the central capsule is especially connected with the complex coordi- 

 nated movements of swimming and of righting when inverted; (c) the axial cords 

 act as both afferent and efferent nerves; (d) the subepithelial bands are also 

 nerves, but their exact function is a special and subordinate one in connection with 

 the ambulacral tentacles and epithelium; (e) evisceration apparently causes but 

 little inconvenience to the animal, and the visceral mass is regenerated completely 

 in a few weeks' time. 



COLOR OF CRINOIDS. 



Of all the animals in the sea there are none that exceed in beauty of coloration 

 the shallow-water crinoids. Flowerlike in form and almost flowerlike in the 

 fixity of their habit, they are also flowerlike in the variety and distribution of 

 their pigments. But with depth the diversity of hue diminishes, so that we find 

 the color range of the deeper water species relatively restricted, while the indi- 

 viduals themselves, losing the almost universal spottings and bandings of the 

 littoral types, become comparatively plain. 



Though crinoids resemble flowers in the diversity and brilliance of their colors, 

 their color types are quite the reverse of flower-like. In a particolored flower the 

 center or eye is more or less abruptly lighter or darker than the remaining por- 

 tions, or the petals are longitudinally striped ; cross banding of the petals is very 

 rare. Among the crinoids particolored species are usually cross banded, regularly 

 or irregularly, and though the pinnule tips may be of a different color from their 

 bases, a true longitudinal striping of the arms is very rare, and a conspicuous eye 

 is never developed. 



