STUDIES OX THE ECTOPARASITIC TREMATODES OF JAPAX. 45 



0. The MesenchijDia. 



The mesenchyina of the Trematocles has been variously described 

 by different autliors. The tact is that it presents ^■ery different aspects 

 in different species and even in different parts of tlie same specimen. 

 The mesenchyma of the mon(jgenetic Trematodes is, generally speak- 

 ing, of very different appearance from the typical form of the same 

 tissue in the Dio-enea, Avhich consists of larii'e vacuolated cells, between 

 Avhich fibrous network with small nuclei is present^^; and varies 

 from a truly cellular character to that of the typical, reticulated, 

 tibrous connective tissue on the one hand ;uid a true syncytium on 

 the other. 



The general mesenchyma of the body has been distinguislied bv 

 certain writers into two parts, for wliicli different names have been 

 ])roposed by different Avriters, but the terms proposed lately l)y 

 ]jrandes,"^ viz. endo- and ectoparenchyma are the simplest and 

 therefore tlie most convenient. In Axine heterocerca these two ptrrtions 

 are very distinctly separated from each other by a tliin membrane of 

 compact connective tissue, and are very (bfferent in character (PL 

 VIII, fig. 1). The ectoparenchyma is, in this species, again dis- 

 tinguishable into two layers, that in which the longitudinal fibres lie 

 and that in which the diagonal and the circular fibres run. TIk^ 

 inner layer, i.e., the one in which the hmgitudinal fibres run. is, in 

 some places, as thick ;is 20 U. a.nd its connective tissue consists of very 

 fine, anast(3m(jsina' fibres, which are but slio'htlv stained in haema- 

 toxylin, and in the knots of which nuclei are here and there present. 

 The ireneral course of the connective tissue fibres of this laver is at 



1). Leuckart— Die thierischen Parasiten ties Menschen. II. Aufl., I. Bd., 3. Lief., p. 13 

 et ^cq. 



2). Brandes— Z. c, p. 424. 



