2 L. MURBACH. 



are in the bases of the tentacles, due apparently to refraction and 

 reflection from brown pigment granules in the free ends of the 

 endoderm cells of the tentacle insertion. As I • understand that 

 "basal bulbs " refers to the enlarged proximal ends of tentacles, 

 or bulbs into which the tentacles are inserted, I do not use this 

 expression. 



To these marginal papillae, under the name of marginal bodies, 

 Yerkes 1 ascribes a special light- recipient function ; he says, " the 

 probability is strong that they are the special organs of photic 

 stimulation." This conclusion seems to be based on the location 

 and heavy pigmentation of the papillae, and also on some experi- 

 ments which will be referred to farther on. 



In the Challenger Report on the Deep Sea Medusae (Vol. IV., 

 p. lii), Haeckel said : "As experiment showed, it is principally 

 the swollen bases of the tentacles which bear such pigment eyes, 

 and that chiefly in the order of the Anthomedusae and in those 

 Leptomedusae which have no marginal vesicles. Such ocelli are 

 more rarely found in Trachomedusae, Narcomedusae, and Stauro- 

 medusae." Again he says : " Moreover medusae perfectly devoid 

 of color which have neither marginal ocelli nor other pigment 

 spots, are sensible to light ; in this case it is probably the sense 

 epithelium of the umbrella margin which discharges this function." 



Now wherever there are special structures in the bulbs above 

 referred to by Haeckel there is perhaps, no doubt that they serve 

 for receiving stimuli of some external kind. In the Leptome- 

 dusae and Anthomedusae there are true tentacular bulbs and the 

 pigment spots in them may serve, in the reception of light. On 

 the other hand, in Gonionemus, a trachomedusa, 2 the marginal 

 papillae are not tentacle bulbs and have apparently no special 

 structures for light reception, unless we consider the presence of 



1 Yerkes, Robert M., Ayer, James B., Jr. ('03), " A Study of the Reactions and 

 Reaction Time of the Medusa, Gonionema murbachii, to Photic Stimuli," American 

 Jour. Physiology, Vol. IX., No. 5, 1 903. 



2 While there can be little doubt about some of the positive trachomedusan charac- 

 ters of the jellyfish, Dr. A. G. Mayer has suggested to me that in the light of Goto's 

 careful work (/oc . cit. ) classing it as a leptomedusa renewed examination of the otocyst 

 organs would seem desirable. As this subject merits more space than can here be 

 given I will only say that 1 have prepared new sections and carefully examined a 

 rather large series and am convinced that the otocyst organs are derived from the 

 endoderm. 



