THE BEGINNINGS OF LIFE. 375 



contents.' He first obtained an insight into these 

 structures by observation of their production in the 

 cells of young Spirogyr*, which he had himself developed 

 from large spores. He says: c ln the cells of these 

 young Spirogyra the existing spiral bands are often 

 broken up, and from their substance are formed, in a 

 manner unknown to me, little cells in which a mem- 

 brane can be clearly detected surrounding green con- 

 tents. I call these cells, spore- mother-cells. They soon 

 increase in size, their membrane separating itself from 

 the contents and expanding into a large hollow vesicle. 

 The contents at the same time acquire a yellowish or 

 yellow-brown colour, and separate into a central, denser, 

 yellow-brown nucleus, and a finely-granular mucilage, 

 which surrounds the nucleus and does not entirely fill 

 the space between it and the membrane. This finely- 

 granular mucilage then becomes balled together, in the 

 space between the yellow nucleus and the surrounding 

 membrane, into a single large corpuscle exhibiting a 

 sharply -defined outline, and appearing as a transparent 

 vesicle with finely - granular contents. The new cell 

 thus formed pushes the brown body, as the figures 

 show 1 , out of its central position, against the wall of the 

 parent cell or the spore-mother-cell. The pressure of 

 these two bodies causes the rupture of the membrane of 

 the spore- mother-cell; the transparent cell emerges and 

 moves about independently and freely in the filament 

 cell in the manner of the zoospores.' They moved 



1 Dr. Pringsheim's paper is illustrated by several figures. 



