282 



THE CELL 



the top of the water, two threads lie in contact with one another 

 for an j considerable portion of their length, conjugation occurs 

 between neighbouring cells. As a rule all the cells prepare for 

 reproduction at the same time by sending out lateral processes to- 

 wards each other. These fuse at the point of contact, whilst the 

 separating wall dissolves, and thus transverse canals are formed, 

 which connect the conjugating threads at regular distances, and 



Fig. 153. Spirogyra longata (after Sachs, Fig. 410). To the left, several cells of two fila- 

 ments, which are about to conjugate: they show the spiral chlorophyll bands, in which 

 crown-like arrangements of starch grains are lying, as well as small drops of oil. The 

 nucleus of each cell is surrounded by protoplasm, from which threads stretch to the cell- 

 wall, b, preparatory to conjugation. To the right, A, cells engaged in conjugation: the 

 protoplasm of the one cell is just passing over into the other at a; in b the two proto- 

 plasmic masses have already united. In B, the young zygotes are surrounded by a wall. 



resemble the rungs of a ladder (Fig. 153). The protoplasmic 

 bodies of the cells then contract away from their cellulose wall, 

 and after a time fuse together. 



Differences which in themselves are trifling, but which on that 



