Il8 REPORTS ON INVESTIGATIONS AND PROJECTS. 



Alfred G. Mayer studied rhythmical pulsation in the medusa Cassiopea, 

 the branchial arms of the stalked barnacle Lcpas, the heart of Salpa demo- 

 cratica, and of the embryo loggerhead turtle. More than i,ooo experiments 

 were carried out. It appears that the stimulus which produces rhythmical 

 pulsations in Cassiopea is conducted by the diffuse nervous network or 

 epithelium of the subumbrella, not directly by the muscles themselves. 

 Pieces of subumbrella tissue cut so as to form a complete circuit can be set 

 into sustained pulsation. The waves of pulsation may cross, or trend with, 

 the muscle fibers and pulsation will be sustained provided the circuit be 

 unbroken. Any cut which breaks the circuit instantly interrupts the 

 pulsation and sustained pulsation can not be restarted. This sort of pulsa- 

 tion is maintained by a single originally stimulated point, and whenever 

 the contraction waves return through the circuit to this point they are 

 restimulated and again sent forth through the circuit. 



It is the general role of magnesium to inhibit or restrain pulsation, 

 while sodium chloride, potassium, and calcium unite to form a powerful 

 stimulant producing abnormally energetic, but not long-sustained, pulsa- 

 tion. It is the office of magnesium to restrain this powerful stimulant, 

 and thus to prolong its action indefinitely. Thus a Ringer's solution is 

 only a stimulant; and a certain amount of magnesium is necessary in 

 order to restrain and at the same time permanently sustain pulsation. 



The Atlantic palolo worm {Eunice fiicata) swarmed on the mornings of 

 July II and 12, and the last quarter of the moon fell on July 13, 1906. 

 Experiments to determine the nature of the reaction which causes the 

 swarm were unsuccessful, but will be repeated under better conditions. 

 We now know that the worm may swarm when there is no rise and fall 

 of tide. 



About 150 colored drawings were made of new or rare Siphonophorje, 

 Ctenophor^e, and Medusas. 



On July 24, 1906, the Physalia, Sea Horse, and other Department vessels 

 were safely laid up in the Miami River, and the yacht's license was surren- 

 dered to the custom house. 



I take pleasure in reporting that the property intrusted to my care is 

 in good condition. 



