22 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
as well as the general grayish tint which the body often has, is due to the 
presence in varying proportions of two different sorts of pigment cells. Those 
of one kind, which might properly be called reserve-food cells, may be found 
in the deeper parts of the body of all well-nourished individuals. They are. 
large rounded cells, with an excentrically placed nucleus, their cytoplasm being 
filled with rounded, highly refractive granules often nearly as large as the 
nucleus. By reflected light these granules appear of an orange-brown color, 
Osmic acid browns slightly, but does not blacken them. Corrosive-acetic or 
picro-nitric mixtures make their composite nature apparent. An outer shell 
of darker, brownish substance appears surrounding usually one, sometimes 
two or three perfectly clear spherical inclusions. Perenyi’s fluid, which is 
very strong in nitric acid, if allowed to act for about an hour, destroys almost 
every trace of the granules, the outer shell being the last part to disappear. 
Absolute alcohol acts in a similar way, but more slowly. 
Graf (99) has figured the granules accurately (see his Figures 87 and 102), 
but interprets their structure somewhat differently, regarding the clear portions 
as cavities; hence he speaks of the granules containing them as ring-shaped 
structures. 
I at first supposed the clear portion to be a central core unaffected by the 
killing fluid, but abandoned this idea when I discovered two or more of them 
in different parts of the same granule. It seems to me that the outer part of 
the granule, which possibly contains some fatty material, as the osmic acid test 
indicates, is laid down upon a central core of a different substance which 
dissolves much more readily in acid solutions. So much my preparations 
indicate, but do not prove conclusively. Further study should be given to 
these interesting structures, doubtless a reserve-food product, which reminds 
one of the structures found in the seed of the Castor-oil Bean (Ricinus). 
The second sort of pigment cell found in this species belongs to Graf’s (99) 
category of “excretophores.” They occupy a superficial position in, or just 
under, the epidermis, and are slender, thread-like, branched (structures) of a 
dark-brown color. They are especially abundant in animals which have been 
kept for some time in well-lighted aquaria. Graf believes that pigment cells 
of this sort become detached as leucocytes from the wall of the body cavity, 
take up excretory products in the deeper parts of the body, especially in the 
neighborhood of the blood vessels, and then by amoeboid movements make 
their way to the surface of the body, there to disintegrate. 
b. Rines, Somites, Eyes. 
External rings, rounded. and distinct ; sixty-seven in number, counting two 
narrow rings at the posterior end of the body (64 and 66, Figure 4, Plate a) 
Somites, thirty-four, as in all species of Glossiphonia. Somites VI.—XXIV., 
triannulate (Figure 4); all other somites show more or less abbreviation.! 
1 Throughout the descriptive part of this paper I shall speak of those somites 
which contain fewer than three distinct rings as “abbreviated” or “reduced.” I 
