4 L. MURBACH. 



he adds (p. 302) that animals, whose tentacles were removed in 

 such a way as to destroy the marginal bodies, never reacted to 

 light ; this, casually mentioned, as if it were not important. Yet 

 this should be the crucial experiment. 



Now since the marginal papillae in Goriionemiis are not true 

 tentacle bulbs, and are only connected with the tentacles by the 

 outer layer of ectoderm, and since the tentacles when pulled off 

 by merely seizing them always, in my experience, break off at 

 their bases, leaving the latter, I could not see how the operation 

 above referred to could be performed. It would be possible by 

 seizing papilla and tentacle-base with forceps, but this would re- 

 move the margin of the bell with the nerve ring. 



Problem. 

 These considerations led me to make experiments, first : to 

 determine whether the light reactions oi G onion emus are dependent 

 on stimulation of the marginal papillae, or, second : whether any 

 other set of organs, e. g., the tentacles, the velum, or the gonads, 

 also have this function. 



Methods. 

 The first experiments were made by cutting the papillae away 

 from the margin with fine sharp scissors in such a way as to in- 

 jure as little as possible the adjacent parts. Operated animals 

 were left until they had recovered from the shock, or even for 

 several days, but never long enough to allow the papillae to re- 

 generate. They were always compared with normal animals taken 

 at the same time. Colors were also noted, as was the tempera- 

 ture of the water. In some of the experiments a 5 cm. deep 

 saturated alum solution was interposed between the animals and 

 the sun, but I have found with other experimenters, that this gives 

 no advantage over plain water. The temperature varied no more 

 than from one fourth to one and one half degrees centigrade in 

 any of the experiments during an observation, and since the only 

 purpose was to test the mere reaction of the papillae or other 

 organs, this change in temperature could be ignored. The med- 

 usae were exposed in dishes of white glazed earthenware, in 

 glass dishes, and in dishes with black substratum. It may 



