1 6 WRIGHT AND MACALLUM. ' [Vol. I. 



ual fibres. They were treated with various reagents, in order 

 to determine the presence of nuclei, and to elucidate the struct- 

 ure of the fibres; but no nuclei could be detected in them, nor 

 could any be demonstrated in the course of the transverse bands. 

 We are not, however, inclined on this account to adopt Poirier's 

 view as to their complete disappearance. The ends of many of 

 the muscular fibres have been traced into the so-called subcu- 

 ticular layer, and, as we have observed circular and longitudinal 

 fibres of the investing musculature as well as parenchymatous 

 fibres in connection with cells of this layer, we are inclined to 

 believe that these bands, which are local developments of one 

 or the other of these sets of fibres, have similar connections, 

 although we have not been able to trace them. The connec- 

 tions referred to are illustrated in Fig. 10, ^, from which it will 

 be apparent that many of the cells of the subcuticular layer are 

 in reality the central protoplasmic elements of the muscular 

 fibres, the contractile elements of which form the musculature 

 on which the investing membrane directly rests. Such connec- 

 tions may be most easily demonstrated in the parenchyma fibres, 

 but suitable sections permit of recognition of similar relations in 

 the circular and longitudinal fibres. 



These muscle cells have generally been interpreted either as 

 formative cells of the cuticula, or as unicellular glands, or as 

 ordinary connective tissue elements. Fischer alone appears to 

 have hinted at their real nature. This observer denies the 

 presence of a subcuticular layer of matrix cells in Opistho- 

 trema, but describes the occurrence of fusiform cells in a 

 layer below the subcuticular muscles. These fusiform cells 

 were observed to be in close connection with the muscular 

 fibres, and were always found to be the most numerous where 

 the muscle fibres were most abundant. Leuckart regarded these 

 structures as a species of tendon fibres, or as peculiarly formed 

 parenchyma cells. 



These cells are most favorably observed-immediately beneath 

 the subcuticular muscle fibres. They measure about seven ^.l, 

 are fusiform, with their long axis directed obliquely to the mus- 

 cular layers, and do not resemble connective tissue elements in 

 any respect. Usually there are two fibrils arising from each 

 cell, one always being more strongly developed than the other; 

 when there is only one fibril the cell has a pear-shaped 



