Cytology and Movements of the Cyanophycee. 307 
diffused, but gradually forms into large angular masses of 
irregular shape. 
(7) MorILiry. 
The power of movement among the Cyanophycez is 
quite marked in some forms, and is practically the only 
distinguishing feature between some genera. In Oscillaria, 
the movements are most marked, and may be divided into 
three classes: (a) Creeping or forward movement of the 
whole trichome, by which it propels itself through the water 
in a serpentiform fashion. (0b) An oscillating movement 
throughout the whole trichome, which gives the name to 
the genus. This movement might also be divided into two: 
(1) the general oscillation, and (2) the more rapid flexion 
of the extreme end of the trichome which usually closes 
the oscillation. (c) A spirally twisting movement which 
accompanies the oscillation. Cylindrospermum and several 
others of the Cyanophycee exhibit the first or creeping 
movement above mentioned, while the hormogonia of those 
forms which bear them are free-swimming, sometimes with 
a twisting motion as in Nostoc (77). Such movements 
among plants have been considerably studied, principally 
on Diatoms, and from these, generalizations have been 
made to include other organisms. Several theories are 
advanced to account for the phenomena, but most of them 
seem untenable. Pritchard (64) has given a very good 
review of all of the theories held by different authorities 
concerning the cause of the movements in diatoms, prior 
to 1861, therefore it will be unnecessary to more than glance 
at a few of them here and note their bearing upon the ques- 
tion of locomotion in the Cyanophycez. 
Naegeli (58) explained the motion as caused by osmotic 
currents between the cells and the surrounding water. He 
says: “Since in the course of their process of nourishment 
they take up and secrete fluid stuffs, so the cell must come 
