146 GENERAL BIOLOGY 





FIG. 56. Conjugation of two strands of Spirogyra. The upper cells 

 are just forming the conjugating tube. This has been established in the 

 next couple of cells. In the next two pairs of cells the cell-protoplasm is 

 passing over from one strand to the other. In the lowermost cell this 

 process has been completed, and the cell-contents have fused into a 

 zygote, which secretes a thick wall about itself and becomes a resting 

 spore. 



FIG. 57. Conjugation of Mougeotia. In this form the cell-contents 

 fuse midway between the two conjugating strands. 



The difference between the gametes may be of 

 varying degrees. In Spirogyra, in which the long 



