282 THE CELL 



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

 for any 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 



PIG. lsa.-Spingyn longata (after Sachs, Fig. 410). To the left, several cells of two fila- 



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



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



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



inlar P T t r y niUgati0n - T the right >^' cells en ^ ed in conjugation: the 

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

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



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

 >odies of the cells then contract away from their cellulose wall, 

 and atter a time fuse together. 



Differences which in themselves are trifling, but which on that 



