484 JOSEPH STAFFORD, 



mediary layer between cuticle and external muscle-sheath. It certainly 

 belongs to the underlying parts and apparently gives insertion to 

 numerous muscle fibres. 



Subcuticular muscle sheath. These strata of muscles 

 vary considerably in different regions of the surface, but nowhere do 

 they acquire so much importance in Aspidogaster as in many other 

 Trematodes. This is, doubtless, to some extent, due to the presence, 

 in the former, of a powerful muscular diaphragm. 



In sections that fall through the pharynx can be distinguished 

 in the peripheral musculature a layer of circular fibres lying close 

 under the boundary between cuticle and parenchyma. Following this 

 is a layer of hollow longitudinal muscle fibres of greater size and 

 underneath these two sets of diagonal fibres crossing one another at 

 varying angles. In this district, too, are inner circular fibres, which 

 occur only here and there, and form one or two discontinuous layers 

 shading into the diagonal muscles. Anteriorly, between neck and foot, 

 as well as at the sides of the body, the longitudinal and diagonal 

 muscles are for the most part reflected onto the septum (Fig. 21). 

 Consequently, the peripheral musculature of the foot presents a marked 

 difference from that of the supra-septal body. The outer circular 

 fibres appear to be the only ones common to the whole surface. In 

 sections one finds other fibres near the cuticle but it must be re- 

 membered that parenchyma-muscles come to the surface to find in- 

 sertion. 



In specimens that have lived for about forty-eight hours in 

 methylen-blue the outer musculature can be conveniently studied. The 

 animals are likely to be lacking in transparency but towards the 

 posterior end where there are fewer organs the muscles are plainly 

 exposed. The circular fibres generally appear in pairs separated by 

 a space, the longitudinal radiate outwards and forwards from the 

 excretory pores, and the diagonal fibres do not i)reserve a constancy 

 of direction. All increase in number and closeness of position as we 

 follow them towards the anterior end. 



Parenchymatous system. 



Parenchyma. Directly under the subcuticular system of muscles 

 is found a mass of cells hitherto not observed in Aspidogaster, but 

 frequently described under various designations in other genera. There 

 seems to be considerable difl'ereuce of opinion as to the exact position 

 and nature of this layer of cells. Some authors speak as if it were 



