STUDIES OS THE ECTOPARASITIC TREMATODES OP JAPAN'. 145 



tions have led me to the same conclusion. I have indeed no positive 

 proof of the non-contractile nature of these fibres ; but the indirect 

 evidence which I shall here advance seems to me, when duly con- 

 sidered, too strong to be resisted. 



In the first place, the fibres under question are different from the 

 ordinary muscular fibres of the body and from those of the suckers of 

 the Tristomidae and the Manocotylidae, as well as from those of the 

 anterior sucker of Oncliocotyle, both in optical characters and in 

 reaction towards staining fluids. Thus, these fibres are in the fresh 

 state slightly yellowish in colour and are less refractive than the mus- 

 cular fibres ; and while the latter stain with hsematoxylin usually well, 

 though not deeply, the former remain in most cases totally unstained. 

 There are indeed cases, as in Hexacotyle, in which the fibres of the 

 suckers stain slightly; but they then always stain more weakly 

 than the muscular fibres. They seem also to have a gi-eater affinity 

 for colouring substances when the worm has been preserved some time 

 after its death, and therefore presumably after some post mortem change 

 has set in, as well as in those specimens which have been kept in 

 alcohol for a long time'\ But in nearly all cases the differences in the 

 two respects above specified— refrangibility and reaction towards 

 colouring fluids — are enough to impress one with the idea that the 

 fibres under question must be very different in their nature from the 

 muscular fibres that are found in other parts of the body. For instance, 

 a glance at fig. 4, PL XII, whiclv represents as exactly as I could make 

 it, a portion of the longitudinal section of a sucker of Dididopliora, 

 will convince one of the difference at least in optical characters 1)etween 

 the fibres that constitute the wall of the sucker and the muscular fibres 

 that are attached to it. But in the second place we can trace all the 

 various stages between these fibres and the ordinary connective tissue 



1). In the latter case all the tissues stain more diffusely than when new. 



