I Art. 3.— N. Yatsu: 



species manifested a sudden change in swimming activity when 

 transferred to direct sunhght from the diffused. Most of them 

 ceased to pulsate and settled to the bottom (Berger '00 p. 5), though 

 some did not do so (Berger '00 p. 26). If the glass vessel contain- 

 ing Charyhclea rastonil be brought into the sun, none of it becomes 

 quiescent. The medusae swim about just as calmly as in diffuse 

 daylight. It need hardly be mentioned that they prefer weak to 

 strong light as do other species of cubomedusse, since in their natural 

 habitat they come near the surface of the sea only in the morning 

 and towards evening, most of them going down to a little deeper 

 part during the rest of the day. I do not know where they are 

 at night. This difference in light reaction between the two species 

 may stand in relation to the fact that C. xaymauaca lives in deeper 

 w^ater than C. rastonii. 



II. The rhopalium in relation to pulsation and 

 swimming activity. 



As to the rhopalium it suffices to saj^ that, contrary to Haake's 

 description ('86 p. 555 and '87 pp. 602, 603), the paired eyes 

 persist throughout life in C. rastonii of Misaki, as has been pointed 

 out by other authors in the same species occurring in other 

 localities. 



As- was observed by Conant (Berger '00 p. 8 and p. 29) the 

 part of the rhopalium loaded with the calcareous concretion lies 

 always lowermost, whatever position the medusa may assume 

 during swimming. This can be seen to best advantage by watch- 

 ing fi'om without with a hand lens a medusa, which is held 

 vertically against the inner side of a glass vessel. In rotating the 

 animal so as to bring the mouth upwards it is noticed that short- 

 ly before the rhopalium stalk takes the inverted position, say 



