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THE AMERICAN NATUR A U 'ST. [Vol. XXXV I L 



The " Palolo " makes its appearance in Samoa in the months 

 of October and November during the last quarter of the moon. 

 This is the time of the lowest or spring tides when the reef flats 

 in shallow places are uncovered or only awash, and at this sea- 

 son the sun is nearest to the zenith. I must reserve for my 

 final paper a discussion of the causes of the swarming of the 

 "Palolo" and will only say here that I am inclined to believe in 

 some thermotropic or heliotropic reaction of the eyes borne on the 

 ventral segments of the epitokal part of the worm. These eyes 

 have recently been studied histologically by Hesse 1 on material 

 collected by Kramer. Hesse states that from their structure 

 the eyes probably do not form images, but function rather in 

 reacting to light of different intensities, the direction of light 

 and possibly to different colors. It is significant that these eyes 

 are found only on a few of the posterior segments of the atokal 

 sedentary part and are not well developed ; while on the other 

 hand they are highly dev eloped on all but the anal segments of 

 the epitokal active part which leads such an ephemeral free 



sexual activity throughout the Pacific Islands and where the 

 " Palolo " occurs the season and even the months are named for 

 it. All of the many other kinds of annelids inhabiting the reefs 

 are sexually mature as shown by the extensive collections made 

 by Kramer and myself in Samoa and Fiji and this is true also of 

 the reef fauna in general. The spawning time of the land crabs. 



