106 DUBLIN UNIVERSITY 



stance which attracts notice, in addition to the remarkable length of the 

 cells, is the presence of a narrow pale band, or interruption of the en- 

 dochrome at the centre of each joint, which fact appears to me sufficiently 

 significant to indicate that towards the Desmidiaceae we are to look for 

 its affinities. I will try briefly to describe a joint more closely. Each 

 joint in proportion to its breadth is extremely long, sometimes, though 

 rarely, as many as forty times, averaging, perhaps, from twenty to thirty 

 times longer than broad, and it is nearly cylindrical and quite smooth. 

 (See Plate XI., Fig. 1 .) There are two points of view from which a diffe- 

 rent aspect of the cell-contents is obtained, from thefact of the endochrome 

 being disposed in a longitudinally compressed or flattened band. When 

 the broader diameter of the endochrome is towards the observer, it is seen 

 to fill the entire width of the cell, and having, as before adverted to, a 

 narrow, transverse, pale space at the centre (separating the endochrome 

 into two equal portions), sometimes band-like, but more frequently cir- 

 cular, from the endochrome terminating at each side with a concave out- 

 line. There is a single central longitudinal series of "vesicles" (or 

 bodies similar to those in Closterium, &c), reaching from end to end of 

 the endochrome, and disposed at intervals of somewhere about the dia- 

 meter of the joint, one of these always occupying the centre of the pale 

 space. The bodies which, following the name used by Ralfs for similar 

 appearances in Closterium, &c, I have just called " vesicles," I believe 

 are not truly vesicles, but solid bodies, or corpuscles. Pressure upon the 

 joints obliterates, or rather hides them, causing the endochrome, which 

 before was apparently of an uniform character, to assume a granular ap- 

 pearance ; while a still greater force upon the pressed-out cell-contents, 

 now become somewhat scattered-about, shows these globular bodies, per- 

 haps some not much altered, others cracked or split, and others in frag- 

 ments (Fig. 4). If these were truly " vesicles," or if they were vacuoles, 

 I do not think this appearance could result. Were they vesicles, I ap- 

 prehend that, by careful manipulation, they should be capable of being 

 pressed out either in a collapsed or burst state. Were they vacuoles, I 

 should imagine that pressure would only efface them, and that they 

 would hardly be found in the mass of extruded endochrome, whereas in 

 reality pressure cracks and breaks them, as before stated, into fragments. 

 I think, then, that the endochrome is at first of a very finely granular na- 

 ture, soasto appear homogeneous, or uniform, whenfresh, with this median 

 series of firm corpuscles imbedded, which arc spherical, and of a smooth 



