STUDIES OX THE ECTOPAB.ASITIC TREMATODES OF JAPAN. 45 



5. The Mesenchyma. 



The mesenchyma of the Trematodes has been variously described 

 by different authors. The fact is that it presents very different aspects 

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

 The mesenchyma of the monogenetic Trematodes is, generally speak- 

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

 tissue in the Digeuea, which consists of large, vacuolated cells, between 

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

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

 fibrous connective tissue on the one hand and a true syncytium on 

 the other. 



The general mesenchyma of the body has been distinguished by 

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

 proposed by different writers, but the terms proposed lately by 

 Brandes,^' viz. endo- and ectoparenchyma are the simplest and 

 therefore the most convenient. In Axine heterocerca these two portions 

 are very distinctly separated fi-om each, other by a thin membrane of 

 compact connective tissue, and are very different in character (PI. 

 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. The 

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

 some places, as thick as 20 U, and its connective tissue consists of very 

 fine, anastomosing fibres, which are but slightly stained in haema- 

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

 The general course of the connective tissue fibres of this layer is at 



1). Leuckart— Die thierisobeu Parasiten des Menschen. 11. Axifl., I. Bd., 3. Lief., p. 13 

 et seq. 



2). Btandes— Z. c, p. 424. 



