10 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



way as females. Eisig (1887) describes similar conditions in Noto- 

 mastus, where the sexual elements are discharged by rupture of the 

 body-wall, and states that the lumen of the segmental organs is too 

 small for the passage of ova. Mayer (1900), for his " Atlantic Palolo," 

 says that by series of violent and sudden contractions " the ripe seg- 

 ments are torn asunder at short intervals by the breaking of the cutic- 

 ula, forming large rents through which the genital products escape." 

 This manner of unloading the sexual products accounts for the apparent 

 sudden disappearance of the dense swarms of " Palolo " a short time 

 after their appearance, which was considered as much of a phenomenon 

 as their sudden appearance. 



Each segment of the atokal part bears on its ventral surface a promi- 

 nent circular pigmented spot, deep brown or black in color (Text Fig. 

 1, Figs. 9 and 10, plate 2). They can be traced forward into the atokal 

 region through about twenty segments, though much reduced in size, 

 and paler in color (Fig. 10). They are absent in from two to fifteen of 

 the preanal segments, those colorless, translucent segments that contain 

 no sexual elements. They were first noted by Ehlers (1868) who likened 

 them to eyes in appearance, but looked upon them as the external open- 

 ings of some sort of a longitudinal gland. It was Spengel (l88l) who 

 first estimated their true nature, and speaks of them as " wirkliche 

 Augen." The minute structure of these ventral eye-spots was studied 

 by Hesse (1899) in carefully prepared material collected by Kramer. 

 Although he states that it is improbable that they are capable of forming 

 images, he says : " Es wird also ihre Leistungsfahigkeit auf die Unter- 

 scheidung verschiedener Lichtsintensitaten, vielleicht auch von Farben, 

 und auf das Erkennen der Lichtsrichtung beschrankt sein." Schroeder 

 (1905), who also made an histological study of these eye-spots, asserts 

 that they differ so much in structure from all known eyes that it is not 

 possible to compare them with any. He hints at the possibility of their 

 being light-producing organs. If they were phosphorescent organs it 

 would have been noted long ago, and could not have escaped the eyes 

 of the natives, as the " Palolo " appears in dense swarms at the surface 

 of the water, and in deep darkness. It is significant that these eye-spots 

 occur in a rudimentary form on only a few of the posterior segments of 

 the atokal, sedentary, part of the worm, and are so highly developed on 

 all but a few of the segments of the active, epitokal part. I believe 

 with Hesse that they react in some way to light, or possibly to heat 

 rays. In text Figure 2, I reproduce Hesse's figure of a median section 

 of one of these eyes, which plainly shows their structure. 



