WOODWORTH : THE PALOLO WORM. 7 



part, the " Palolo," that is periodically cast off and leads such an ephem- 

 eral existence, while the anterior atokal part remains in the galleries of 

 the reef-rock to regenerate, by a process of strobilization, a new posterior 

 atokal sperm or egg sac, which at the appointed time is again set free. 

 The sexes are different in color, the color of the male being reddish 

 brown or buff to yellowish, while that of the female is a deep bluish green 

 (Figs. 1 and 2). These colors are very pronounced in the epitokal 

 region, and are due to the sexual elements, ova and sperm. After the 

 discharge of the sexual elements the collapsed integument is colorless and 

 translucent. These distinctive sexual colors are found in the broader 

 anterior atokal region, but not in so marked a degree, the female being 

 only a little more greenish in color than the male, and here the colors 

 are doubtless integumentary (Fig. 3). It is from the deep green color 

 of the ova in the epitokal region that the specific name viridis is derived. 

 Elders (1898) has so minutely and accurately described the worm that 

 it would be superflous for me to quote at length the details written by 

 the master's hand, and I refer the reader to his paper. I can only 

 supplement his description by additional measurements, etc., from more 

 abundant material, and supply some figures. 



The length of the " Palolo," that is the free-swimming epitokal part 

 of the worm, has been variously estimated at from a few inches to three 

 feet, i. e., a maximum of 90 cm. This great length is given by Gill 

 (1854). The longest specimen that I measured in the living condition 

 was 30 cm. This is about the average of the measurements given by 

 seven authors. From alcoholic material, where there is considerable 

 shrinkage, Elders estimated 20 cm, and states that some segments were 

 probably missing. The atokal region comprises about one fourth of the 

 total length of the worm, and the greatest diameter is about 4 mm, while 

 the length of the segments is about \ mm, or about twenty times as 

 broad as they are long. This ratio begins at about the fifteenth seg- 

 ment from the anterior end, not counting the two large cephalic segments 

 (Fig. 3). The ratio of length to breadth of these fifteen segments is 

 about five to one. In the first of the two large cephalic segments the 

 ratio is about two to one, and in the second four to one (Figs. 3 and 7). 

 The broader anterior segments are also marked by a brown pigment 

 which is densest on the dorsal surface, diminishing toward the sides and 

 disappearing toward the ventral surface. It is densest in the two large 

 cephalic segments diminishing posteriorly, and ceases at about the 

 fifteenth segment, where they become shortest (Fig. 3). In one male 

 specimen 429 atokal segments were counted, in another 350. These 



