STUDIES OS THE ECTOPARASITIC TREMATODBS OF JAPAX. 13 



glands ; but on comparing it with another series of sections I was 

 able to demonstrate clearly their muscular nature.'^ 



3. Musculature. 



The musculature of the body of the Trematodes consists, as is 

 well known, typically of four sets of fibres, viz., the circular, the 

 diagonal, the longitudinal, and the dorso-v antral. There are, however, 

 some variations in different species and genera ; and I shall proceed 

 to note ihem i n the species studied by me. 



In Microcotyle, Axine, Onchocotyle, Octocotijle, Monocotijlc, Galicotyle, 

 and Tristomum I find the musculature of the body to consist of the 

 typical four sets of fibres ; but the different sets or layers are developed 

 in different degrees in different species. Thus in Microcotyle, Axine, 

 Octocotyle, Diclidojjluyra, Monocotyle, and Calicotyle, the circular fibres 

 are very fine and are directly applied to the basement membrane, so 

 that they appear in sagittal sections of the worms as minute dots 

 arranged at regular short intervals. In cross-sections of the worms 

 they are very difficult to demonstrate. In Tristomum, on the contrary, 

 the individual circular fibres are stronger and they are generally at 

 some distance from the basement membrane (PI. XXI, fig. 4 ; 1.^1. 

 XXIII, figs. 4 and 7 ; PI. XXIV", fig. 2), leaving a layer of mes- 

 enchyma of variable thickness between. In Onchocotyle and Hexacotyle 

 the circular fibres seem to be entirely wanting. 



In Diclidophora an additional layer of longitudinal fibres comes 

 between the circular and the diagonal fibres (PL X, fig. 4 & PI. XI, 

 -figs. 3 & 5). The individual fibres of this layer are separated from 

 one another by an intervening mass of mesenchyma ; they ai-e usually 

 oval or circular in cross-section and are generally a little finer than 

 those of the inner longitudinal layer. This layer has also been 



1). Compare on this question tte more exhaustive discussions in Monticelli's paper (Primo 

 contributo etc., p. 202 et infra). 



