PEOCEEDIlSrGS OF THE NATIONAL MUSEUM 



VOL, 76 



also does not occupy exactly the anterior pole, but lies slightly on 

 the right side of the median plane. Consequently the parasite is 

 not completely bilaterally symmetrical. Except the central part of 

 the mesentery, which surrounds the stalk, the whole of this organ 



h 



Figure 4.— Briarosaccus callosus, visceral mass, right surface. The 



SOLID line delimits THE PART FROM WHICH SECTIONS HAVE BEEN MADE, 

 THE LINE a LOCATES FIGURE 6, AND 6, FIGURE 5 



constitutes a narrow strip of tissue connecting the visceral mass with 

 the mantle. The central part is much broader; here a quantity of 

 strong muscles are present which fasten the visceral mass to the 

 shieldlike portion of the cuticle round the stalk. As in other Rhizo- 



^^^y^'f^S' >-,<«f 





r^', 

 ^'^s. 



'^, 



Figure 5. — Briarosaccus callosus, part of a transverse section h in figure 4, showing the 



TESTES. X 7 



cephala, the mesentery contains large lacunae, one of which is in 

 connection with a spacious lacuna found in the posterior region and 

 in the median plane of the ventral surface of the mantle. In the 

 anterior region this lacuna terminates in the sphincter of the mantle 



