22 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



as well as the general grayish tint which the body often has, is clue to the 

 presence in varying proportions of two different sorts of pigment cells. Those 

 of one kind, which might properly be called reserre-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 brgwns 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 theu- structure somewhat diflerently, 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 unaff'ected by the 

 killing fluid, but abandoned this idea when I discovered two or more of them 

 in difi'erent 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 Grafs ('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. 



h. Rings, Somites, Eyes. 



External rings, rounded and distinct ; sixty-seven in number, counting two 

 narrow rings at the posterior end of the body (64 mid 66, Figure 4, Pluti; 2). 



Somites, thirty-four, as in all species of Glossipbonia. Somites vi.-xxiv., 

 triannulate (Figure 4) ; all other somites show more or less abbreviation.' 



^ 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 



