No. I.] SPHYRANURA OSLERL 1 5 



to Salensky^ every muscular fibre belonging to the parenchyma 

 of Amphilina represents a muscle cell in which two elements 

 can be distinguished ; a cortical layer (Rindenschicht) and a 

 medullary substance (Marksubstanz). The first forms the 

 greater part of the fibre, at the extremities of which it splits 

 up into fine fibrillae, difficult to follow, but terminating in the 

 peripheral muscular layers. The medulla forms on the course 

 of the fibre a large swelling, which, when viewed from certain 

 directions, is spoon-shaped, and which contains a granular proto- 

 plasm and a nucleus, the latter being larger than the surrounding 

 nuclei. The cortical layer, except at the swollen part, encloses 

 the medulla ; at that point, however, to which the medulla is 

 confined, the latter protrudes through a longitudinal, slit-like 

 opening in the cortex. 



Chatin^ describes each muscular element as consisting of a 

 central protoplasmic body, with a distinct nucleus from which 

 irregular processes arise ; one of the latter becomes consider- 

 ably prolonged and strongly developed in such a way that the 

 protoplasmic body appears of accessory or minor importance. 

 Chatin asserts that these muscular fibres are like those of Nema- 

 todes and of Amphilina. 



Poirier^ found, in the parenchyma of young Distomes, cells 

 presenting all stages, transitional from that of the ordinary cell 

 to that of a fully formed muscle fibre. These cells have a deli- 

 cate envelope and a granular protoplasm which stains feebly, like 

 muscle fibre, with picrocarmine. They elongate gradually, and, 

 when in groups, in a direction parallel to each other. During 

 this elongation the walls of the cell thicken, and the granular 

 protoplasm condenses in the axis of the prolongation and finally 

 disappears. The same fate is eventually shared by the central 

 part of the cell and its nucleus. 



The caudal muscular bands of Sphyranura, and especially 

 the longitudinal ones, which are generally over two millimeters 

 in length, offer favorable material for the study of the individ- 



' Salensky. Ueber den Bau und die Entwickelungsgechichte der Amphilina. Zeit. 

 wiss. Z06I., XXIV., p. 306. 



'^ Structure des Elements musculaires chez les Distomiens. Bull. Soc. Philomath. 

 Paris, Tome 6, 1882, p. 200-202. Abstract in the Zoologischer Jahresbericht for 

 1883, Abth. I., p. 160. 



'Arch. Zool. Experiment. 2ieme Series, Tome III., p. 492-4. 



