JAPANESE PALOLO, CERATOCEPHALE OSAWAI, N. SP. 21 



in length, and 3—11 mm. in breadth at the broadest part, while 

 the number of segments varied from GO to 78. In the females, 

 the length varied from 35 mm. to 120 mm., and the breadth 

 within nearly the same range as in the males ; the number of 

 segments was G0-74. In general it may be said that the atoca 

 in developing into the epitoca increases about three-fold in greatest 

 breadth, but decreases by nearly one-half in length, while the 

 number of segments is reduced by approximately two-thirds as 

 already indicated. The segments, taken singly, have grown not 

 only in breadth but also considerably in length, and consequently 

 have become more distinct than before. 



Color. — In the epitocous phase, the sexes are as before 

 mentioned casilv distinguishable in color. In the females the 

 body is at first of a yellowish color (PL I., figs. 6 B and Gb), 

 but after swimming about for a while in exposure to light, the 

 color changes to a light greenish (PL I., fig. 7). The males are 

 pinkish white blending into a deep pink at the bases of the 

 parapodia (PL I., figs. G A and 6 a). 



Cephalic Region. — There exists no remarkable difference in 



the cephalic region in the two phases, except in regard to the 

 eves. It will therefore not be amiss here to give first a short 

 description of an eye in the atocous phase. It consists of the 

 three chief parts : retina, lens and cornea. The retina is composed 

 of pigmented cells, each being in possession of a clear refractive 

 end, the rod. The retinal cells collectively make up a pigmented 

 single-layered epithelium, forming the wall of a deep cup, the 

 aperture of which represents the pupil. This is not conspicuously 

 discernible from the outside, being covered over bv the cuticula 



