ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 435 



difference of length and diameter in the conjugating cells, that 

 deemed the female being the larger. The protoplasmic contents pass 

 only in one direction, and the change first commences in the chloro- 

 phyll-bands of the supposed male cells, with accompanying contraction 

 of the protoplasmic contents. The genera Mesocarpus, Staurospermum, 

 and the doubtful form Craterospermum, on the whole substantiate the 

 view above enunciated of sexuality. 



Movements of the Oscillarieae.* — In addition to the oscillatory 

 movements of the Oscillarieae, creeping and rotating movements of 

 the protoplasm are also to be perceived, especially in those species where 

 the cell-wall is thin and flexible, as Oscillaria tenerrima and cerughieo- 

 ccerulea. These have been more closely investigated by A. Hansgirg. 

 The oscillating motion commences as soon as the filament has 

 become fixed to a substratum by means of the mucilaginous 

 substance excreted on the surface of the cell-wall. This extremely 

 thin layer of mucilage often forms a hollow tube behind the creeping 

 filament. It is not coloured brown by iodine like protoplasm, and 

 takes only a passive, not an active part in the movement of the fila- 

 ment. The motive power which causes the gliding motion of the 

 filament on a solid substratum resides in the protoplasmic contents 

 of the cells, and is connected with osmotic currents. 



In the protoplasm which had escaped ' from the broken end of a 

 filament of 0. princeps, the author observed a number of amoeboid cells, 

 from 9 to 12 /A in diameter, nearly spherical in form, and putting out 

 colourless pseudopodia about twice the length of the central body, 

 and to these he attributes the motile power of the protoplasm of the 

 filament. The so-called "cilia" which proceed from the terminal 

 cells of the filament of 0. cerugineo-ccerulea, do not participate in its 

 motion except passively, and are, according to the author, inde- 

 pendent parasitic organisms of the nature of LeptotJirix. 



In all the cells of the filaments of Oscillaria, the turgidity is 

 unusually great, and the dividing septa experience great differences 

 of pressure from variations in the tension. The cause of the oscillating 

 motion appears to be that the protoplasm takes up water more 

 rapidly, and consequently swells to a greater extent, than the enve- 

 loping sheath of mucilage. Several species can retain their vitality 

 to an extraordinary extent, and for a long time after losing their water 

 and becoming completely dried up. 



A series of experiments made with a variety of substances led 

 the author to the conclusion that the movements of the Oscillarieae 

 are caused mainly by the osmotic forces and forces of imbibition, 

 which act on the protoplasmic contents of the cells, and not to any 

 external layer of protoplasm. In those species where the filaments 

 are inclosed in an osmotic mucilaginous sheath, in which they move 

 alternately backwards and forwards, this takes place chiefly by 

 osmotic processes in the protoplasmic contents of the cells, in con- 

 sequence of which the turgidity becomes greater alternately in the 



* Bot. Ztg., xli. (1883) pp. 831-43 (1 pi.). 



2 G 2 



