356 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



0.0045 mm. in thickness, but which are only 0.008 mm. long when contracted. 

 Ludwig believed that the terminal hairs described by Perrier were nothing but 

 secretion products. 



Cuenot confirmed the existence of the axial muscle fiber noticed by Perrier 

 and discovered its nucleus. 



Jickeli described the papilla? as composed of the extensions of three or four 

 epithelial cells with nuclei at their base, the distal ends of each carrying a fine 

 sense hair. He noted the existence of a slowly waving flagellum projecting be- 

 tween the three or four terminal sense hairs, which he considered a prolongation 

 of the median fiber described by Perrier. 



Miss Irene Sterzinger noticed mucus at the tip of the tentacles, but was not 

 able to demonstrate its occurrence in the papillae. 



Reichensperger, whose description of the papillae is given above, found that 

 the waving terminal flagellum described by Jickeli is merely an optical effect due 

 to the secretion from the gland cells escaping into the water. 



Perrier, Mobius, and Gotte considered the papillae as sense, or tactile, organs; 

 Ludwig, with great diffidence, suggests that they may be single-celled glandular 

 organs; Jickeli denied the presence of a secretion in the papillae and described 

 them as purely sense organs; Miss Sterzinger suggested that the mucus glands 

 in the tentacles may be connected with the procuring of food. 



Reichensperger noticed that the secretion of the glands at the base of the 

 papillae differs markedly from that of the epithelial gland cells, and from that of 

 the cement-secreting cells, and is not of a purely mucoid nature. He believes that 

 the papillae are defence organs, analogous to the nettle cells of actinians. When 

 the terminal hairs are touched the papillae contract, pouring out their secretion into 

 the water. This secretion is of such a nature that by it large animals are prevented 

 from reaching the soft parts of the animal, while small organisms, small crus- 

 taceans and the like, are benumbed or killed, and subsequently carried by the cilia 

 of the ambulacral epithelium to the mouth. 



DORSAL CLAUDS. 



On the dorsal side of the calyx, on the sides of the arms and pinnules, and also 

 beneath the epithelium of the anal tube in N eocomatella pulcfiella, Hamann found 

 more or less egg-shaped cell groups. These groups, each composed of five or more 

 individual cells, occur directly below the epithelial layer. The single cells are 

 vesicular, possessing a thin membrane inclosing the clear, watery fluid which does 

 not stain; a spherical nucleus is visible lying more or less centrally surrounded 

 by a small amount of cytoplasm which is stretched out pseudopodia-Iike to the 

 cell walls and holds the nucleus in position. When isolated the walls of these 

 cells are often much folded. 



Similar cell groups were found in the walls of the pinnules in all the comas- 

 terids studied by Hamann, but they were not met with in any endocyclic species. 



