REMARKABLE SPECIES OF ECIIIUROIDS. 15 



ing several large and small vacuoles only. By a careful obsei vjition 

 of serial sections I have come to the conclusion that the several 

 young sperm-masses are attached to the mesentery-like band for 

 the moi^t part in :i single row, which, however, is not quite con- 

 tinuous, but is interrupted at intervals by gaps, presumably left 

 behind by the falling off of the riper masses into the body-cavity. 

 I am thus led to endorse Spengel's ('79) view, so far as it goes, 

 that the floating sperm-masses originate from the innermost layer 

 of the body-wall, i.e., from the peritoneum. However, in the 

 male studied by me, they certainly do not arise from all over 

 the latter, contrary to the opinion maintained by some investigator. 

 The formative region is strictly confined to a narrow streak in 

 the peritoneum, along the median line of the ventral body-wall. 

 Thus, it is interesting to note, the testis presents a far reaching 

 degree of identity with the ovary of the female, not only in 

 origin and position but also to a certain extent even in structure. 



The Coelomic Corpuscles. — Besides the above described sperm- 

 masses, the coelomic fluid contains an abundance of free cells or 

 coelomic corpuscles (figs. 14 and 16, b.c.). Spherical or ovoid in 

 general shape, the finely granular cytoplasm shows a nucleus 

 which is full of deeply stained chromatin. They are especially 

 numerously present in the posterior and anterior parts of the 

 body-cavity, being at some places so closely packed together as 

 to present an irregularly polygonal shape. 



The principal features of Bonellia 7niyajimai may be sum- 

 marized as follows : 



The female. Body short, cylindrical, narrowed towards both 



