12 Dr. M. Schultze on the Terrestrial Planarise. 



more darkly granular, until the racemose extremities of the 

 intestinal ramifications, which are attached to the inside of the 

 annular cutaneous muscles, are formed exclusively of the epithe- 

 lial cells, only surrounded by a delicate structureless membrane. 

 These largely cellular extremities of the ramified alimentary tube 

 may be compared to a liver in their function. 



The muscular fibres of the alimentary canal are for the most 

 part similar to those of the skin above described. Besides these, 

 however, there are other muscular elements in the entire extent 

 of this system of canals, and these are not dissimilar in form to 

 the organic fibre-cells of the higher animals. They are usually 

 fusiform, flattened bodies, with rounded or irregularly torn ends, 

 of a similar size and form with the broad, short fibre-cells of 

 arterial membranes, which I have figured in my Inaugural Dis- 

 sertation '^De arteriarum notione, structura," &c., 1849, tab. 3, 

 figs. 2 & 4. They are transparent, pale, colourless, and not 

 granular, but, on the other hand, are provided with an indica- 

 tion of longitudinal striation ; they are homogeneous or exhibit 

 a granular central streak, which either runs through the whole 

 length of the fibre-cell-like body, or is only perceptible for a 

 short space in the centre. This streak always possesses a swelling 

 in the middle and is pointed at the ends ; it has, however, no 

 similarity to a sharply defined nucleus, but rather resembles the 

 granular axial cords of the muscular filaments of the Mollusca 

 which C. Semper has recently described (Siebold and Kolliker^s 

 Zeitschr. viii. p. 345. tab. 7. fig. 10). The form of the bodies 

 described varies in many ways. Although the spindle-shape is 

 the most usual, a few clavate bodies occur, which are drawn out 

 at one extremity into a long filament ; others resemble fragments 

 of fibres, and others again represent actual long fibres, but at 

 the same time, in their refractive power and the indication of the 

 longitudinal striation, perfectly resemble the fusiform bodies, 

 although their breadth is less, so that a transition of the one 

 form into the other cannot be mistaken. All these elements 

 occur in the walls of the alimentary tube mixed with narrow 

 muscular fibres, such as I have described as situated in the skin, 

 and to these again they exhibit distinct transitions, so that, for 

 this reason especially, I do not hesitate to draw a conclusion as 

 to the muscular nature of the fusiform bodies. It appears, 

 therefore, as though the broadest of the muscular bands in the 

 body of my Geoplana were composed of single elements similar 

 to the fibre-cells of the higher animals, which after maceration 

 may be easily isolated, or readily break away where they were 

 previously firmly united, whilst the narrower ones form long, 

 continuous filaments in which a coalescence of several cells is no 

 longer to be perceived, or has never existed. 



