STUDIES OX THE ECTOPARASITIC TREMATODES OF JAPAN. 3]^ 



u very narrow, secondary zone of niiicli refractive power and M-ell 

 stained in huematoxylin. Tliis zone is so narrow tliat it appe;irs only 

 as :i fine line, and its refractiveness and capacity of being stained witli 

 liaematoxylin are niucli inferior to tliose of the primary zone. I liave 

 o])served some of tliese fibres l)ifuroating towards one of tlieir ends 

 (PJ. XVII, figs. 7 and 12). 



The stri])ed fil)res ab(^ve descia'iDed are ad most uniformly dis- 

 tril^uted in the secants into Mhicli the sucker is divided, as well as in 

 tlie radial elevations themselves. In the latter, the fibres lie at riglit 

 angles to tlieir length, and are consequently very short (PI. XA^II, 

 fig. 8). They may also be entirely absent frc^n them for a more or 

 less wide extent (PL XVII, fig. 3). On the other hand, they are whoU v 

 absent from those parts of the sucker which lie below the radial eleva- 

 tions. Here the sulistance of the sucker is entirely formed of connect- 

 ive tissue, the fibres of wliicli unite into bundles on the ventral side 

 in such a way as to form a series of window-like cavities (PL XVII, 

 fig. 3) ; while on the dorsal side the fibres form generally a compact 

 network, leaving only here and there a number of large cavities. The 

 centre of the sucker is whollv devoid of striped fibres, and is sharply 

 defined from tlie surrounding parts l)y a membrane of connective tissue 

 (PI. X\"ir. figs. 4 and 5). Tliis central part is traversed by the terminal 

 portions of some of the longitudinal fibres of the body, which are here 

 formed into bundles and are inserted, some into the very centre of the 

 sucker, others more periphera.lly into the membrane of connective tissue 

 that separates the centre of the sucker from the surrounding parts. 



As may be inferred from the above description, the sucker of 

 Mofwcotijle is di^'ided l)oth externally and internally int(3 eight equal 

 secants — externally l\v radial elevations, a.nd intern:dly liy correspond- 

 ing radiating se[)ta formed of fibrous connective tissue and wholly 

 destitute of striped nuiscular fibres. 



