BIOLOGY, MARINE — MAYER. I23 



Medusa, or parts of the margin containing sense-organs, cease to pulsate in 

 this solution in less than 6 minutes. The marginal sense-organs can not 

 send forth stimuli producing contractions unless they be constantly supplied 

 with calcium from the sea-water, whereas the disk itself is relatively inde- 

 pendent of the calcium of the sea-water. 



On the other hand, both the disk and the perfect Medusa will pulsate in 

 sea-water saturated with CaS04. The pulsation of the disk is therefore not 

 dependent upon a definite and precise proportion between the calcium and 

 the Na and K of sea-water, as was claimed by Loeb to be the case in 

 Gonioiiemus. 



1CO2 dissolved in sea-water quickly paralyzes the disk, but has little effect 

 upon the marginal sense-organs. 



Cassiopea will pulsate fully half an hour in a pure ^ normal NaCl solution, 

 but is almost instantly stopped in an isotonic solution of Na-COs. Indeed, it 

 pulsates longer in LiCl than in Na^-COa. Evidently the salts themselves 

 as well as their ions have much to do with pulsation. This is opposed to 

 Loeb's view. 



If the otolithic masses of the marginal sense-organs contain combinations 

 of Na, Ca, K, and Mg (such as K2Ca,Mg(S04)6, K.Ca(S04)2, KoCa, 

 Mg(S04)4, orKiMgCSOi)-), and if potassium be constantly dissociating 

 the disk would be set into contraction by the free K2S04. Then if this con- 

 traction caused the K-SOi to again combine with the Ca or Mg, or to 

 dissolve out into the sea-water or into the gastro-vascular space, the stim- 

 ulus would cease and no other contraction would follow until more potas- 

 sium salt was set free. Preliminary experiments indicate that some such 

 reaction may possibly take place in the otolithic masses, but I am not yet 

 prepared to assert it as a fact. It would readily account for the slow, fairly 

 regular control of the sense-organs over pulsation. 



The paper of which the above is a partial summary will appear 

 as a bulletin of the Carnegie Institution. 



Report upon the Nature of the Stimulus zvhich Produces the Si^'arm- 

 iiig of the Atlantic Palolo, by Alfred G. Mayer. 



For five years the Atlantic palolo worm, Eunice fucata, has been seen to 

 swarm in great numbers upon the surface of the sea at Tortugas, and to cast 

 out its genital products, early in the morning of a day within three days of the 

 time of the last quarter of the July moon. This year (1905) the worm 

 swarmed in vast numbers on July 22, and smaller swarms occurred on July 21 

 and 23. The last quarter of the moon fell on July 24. What was more remark- 

 able, however, was the fact that a small swarm also occurred on July 9. 1905, 

 and this was the day of the first quarter of the July moon. The worm was 

 seen upon no other morning, although the ocean was watched constantly from 

 April 22 to July 26. Evidently, then, the worm tends to respond to the first 

 as well as to the last quarter of the moon. 



As is well known, the complete worms live in cavities in the corroded and 

 dead coral rock, or coquina, and on the morning of the swarm the posterior 

 extremity is cast off and swims upon the surface, traveling with the posterior 

 end moving forward and twisting in the direction of the hands of the clock, 

 when viewed from the broken anterior end of the swimming part of the worm. 



