8 bulletin: museum of comparative zoology. 



counts are not accurate owing to a dense gelatinous secretion in the 

 posterior part, which makes it difficult to count the very short segments. 

 The region of this secretion, in the longest of the atokal specimens, 

 began at about segment 300 and extended backward to the narrow 

 epitokal region. The transition between the broad atokal and attenu- 

 ated epitokal regions is abrupt and very marked (Text Fig. 1 and Fig. 10, 

 Plate 2), owing to the difference in diameter and shape of the segments 

 and the difference in color due to 'the sexual elements in the epitokal 

 segments. The diameter of the epitokal segments is, in general, slightly 

 more than 1.50 mm in alcoholic material, and the length is about the same. 

 In the living animal the length of the segments is slightly more than 

 the breadth. The epitokal region has somewhat the appearance of a 

 string of beads, the segments being rounded, bulging at the middle and 

 constricted at the dissepimental zones (Text Fig. 1). As has already 

 been mentioned, the epitokal region is but an egg or sperm sac and leads 

 but a brief free existence, and as will be seen later, the rounded, plump 

 shape of the segments can be explained by the suppression of organs due 

 to the crowding effect of the sexual products. Beginning at about the 

 fifteenth from the posterior end, the segments become narrower, and 

 more flattened so that the posterior end tapers to the last or anal seg- 

 ment. Varying from two to fifteen in number, the preanal segments 

 are colorless and translucent, not containing any sexual elements 

 (Fig. 9). The cephalic and anal cirri (Figs. 3 and 9), the chsetae (Figs. 

 13 and 14) and the jaw apparatus (Figs. 11 and 12), are characteristic 

 of the genus, and have been minutely described by Elders. The great 

 length of the cirri on the first pair of parapodia described by him is 

 plainly seen in Figure 3. Ehlers finds many resemblances between 

 Eunice viridis and E. siciliensis Gr. in which species there is also, at 

 sexual maturity, an intensification of the color in the posterior region. 

 With Ehlers, I found the gill filaments in the atokal region to begin at 

 about the 135 th segment. They attain their greatest length at about 

 segment 175. The presence of gill filaments in the epitokal part is 

 difficult to determine. When they are present they are much aborted, 

 and there is no particular region where they can always be found. 

 They are constantly absent in the empty, translucent, preanal segments. 

 Ehlers believes that where the gill filaments are lacking in the epitokal 

 region they have been lost, " abgefallen," due to their slight union with 

 the dorsal cirrus, and that the loss of them may be due to one of the 

 regular processes involved in the life of the "Palolo." This is in 

 accord with other processes that take place, such as the general histol- 



