On Some Points in the Organization of 



Ceratocephale osawai Iz. 



BY 



Akira Izuka. 



Science College, Imperial University, Tokyo. 

 With Plate XL L. 



While engaged in the study of the Japanese Paiolo {Ceratocephale 

 osazvai*) I have noticed in the internal organization of that worm some 

 points which I think may be worth while to put on record. 



The worms were killed with saturated solution of corrosive sublimate 

 with an addition of little acetic acid, with Merkel's fluid or with v. Rath's 

 killing solution. The last named fluid was used especially for the study of 

 the nervous system For staining, borax-carmine, eosine, safranin, gentiana- 

 violet, orange-G and glycerine haematoxylin were used. 



1. Of the Circulatory System. 



The blood contains numerous red-colored corpuscles of a flat, 

 biconvex, elliptical shape, measuring 15//. in the longer and \2n. in the 

 shorter diameter. Plate XII, fig. 6 shows the corpuscles in lateral view, 

 and fig. 7 the brownish yellow hajmin-crystals prepared from the blood and 

 the manner in which they are often grouped together 



Of the blood-vessels, the dorsal vessel (fig. 1, cl. v ), as seen in trans- 

 verse sections of the worm, occupies a position beneath the circular 

 muscle (c. ;//.), between the two dorsal longitudinal muscles {d. I. 111 ) and 

 somewhat nearer to the skin than to the intestine. In it the blood 

 traverses postero-antcriorly as is evident from the direction of the peristalsis 

 distinctly observable in the living worms. 



The ventral vessel (v v ), which springs in the fourth segment and 

 reaches down to the anal segment, runs between the ventral nerve-cord 



* lour. Sci. Coll., vol. XVII. Art. II. 



