106 T. H. JOHNSTON. 



neck that these structures are best developed, whilst as 

 we pass further back, they are less marked and are hardly 

 distinguishable at all in mature proglottids. They are 

 present on the cuticle lining the suckers. In transverse 

 sections the cuticle is seen as a comparatively thick layer, 

 immediately below which is a very well marked basement 

 membrane separating it from the parenchyma (fig. 4). 



The parenchyma is very loose in structure. The cortex 

 is somewhat narrow and does not contain any calcareous 

 corpuscles, these bodies being absent in this species. In 

 the outer region of the cortex and immediately below the 

 basement membrane is a very well defined layer of sub- 

 cuticular cells, which are readily stained. They occupy 

 nearly half the cortex. 



The various parts of the musculature are not well 

 developed. The dorso ventral fibres which may be seen 

 passing through the parenchyma to be inserted into the 

 dorsal and ventral cuticle, are very delicate and few in 

 number. The transverse muscle fibres which are situated 

 between the medulla and the cortex above and below, and 

 pass out laterally for insertion, are also very weak. The 

 main longitudinal muscles are comparatively small. They 

 are arranged in two concentric sets, each being made up 

 of a large number of small bundles, all of which are about 

 the same size. The whole strobila is thus not very 

 muscular and consequently does not undergo much alter- 

 ation by contraction. The nervous system consists of a 

 small longitudinal nerve on each side of the strobila in the 

 medulla and just external to the ventral excretory vessel. 



The excretory mechanism is represented by a dorsal and 

 a ventral longitudinal vessel on each side, and by a trans- 

 verse vessel which connects the ventral vessels of opposite 

 sides, near the posterior border of each segment. No 

 valvular structures were recognisable. The longitudinal 



