438 PRACTICAL BOTANY 



red spot, and a slowly pulsating vacuole : each cell is 

 furnished with two cilia, which project heyond the 

 surface of the ccenobium : these are better seen after 

 staining with iodine. 



2. The fine threads of protoplasm, also seen more 

 distinctly after staining, which traverse the swollen 

 cell-walls, and connect the cells together as a con- 

 tinuous network. 



3. At the extreme outer surface of the ccenobium 

 note a more clearly defined membrane, marked off into 

 polygonal areas corresponding to the cells : in this is 

 the swollen gelatinous substance which fills the whole 

 cavity of the coenobium. 



4. The cells which form the daughter-ccenobia : 

 these may be recognized as of larger size than the 

 rest, the protoplasm being denser. Observe in different 

 specimens their various stages of division, first into four, 

 then into eight cells : the disk-like group thus formed 

 becoming convex (by reason of quicker surface-growth 

 at the centre than at the periphery), and gradually 

 assuming the form of a hollow sphere, which projects 

 into the cavity of the parent : the pore, corresponding 

 to the margin of the original disk, may be seen after 

 the young coenobium has assumed the spherical form, 

 and even when it has attained a considerable size. 



During the summer nothing further will be observed as to the 

 mode of reproduction of Volvox beyond that vegetative propaga- 

 tion above described, which is repeated through a series of 

 generations ; but in the autumn sexual organs may be formed, 

 the antheridia and oogonia being borne on the same individual 

 in V. globafor, and are easily distinguished from one another, 

 and from the neutral cells of the crenobium. 



i. The antheridia are to be recognized as enlarged cells with 



