214 



FOUNDATIONS OF BIOLOGY 



shifting of individuality from the cells to the colony as a 

 whole. This specialization is exhibited chiefly with regard 

 to reproduction and reaches its highest expression among 

 colonial PROTISTA (Protozoa and Protophyta) in VOLVOX, 

 where among ten thousand or so cells, perhaps a score are 

 specialized for reproduction and the rest are vegetative. 

 Usually each of the reproductive cells (germ cells) divides 



A. Paramecium. 



CELL DIVISION 



(Binary Fission) 



An indefinite number 



of generations 



TEMPORARY 

 CONJUGATION 

 (Fertilization) 

 Each cell fer- 



CELL DIVISION 

 (Period of Re- 

 construction) 

 Each fertilized 



tilizes the other, cell gives rise to 

 four typical 

 animals. 



CELL DIVISION 

 (Binary Fission) 

 An indefinite 

 number of gen- 

 erations, 

 etc. 



B. Volvox. 



CELL DIVISION CELL DIVISION CELL DIVISION PERMANENT CELL DIVISION 

 (Colony for- (Asexual Re- (Gamete for- CONJUGA- (Colony forma- 



mation) production) mation) TION tion) 



Zygote (z) de- Germ cells (g.c.) Certain germ (Fertilization) Zygote develops 

 velops into a give rise to new cells produce One sperm into a colony, 

 colony. colonies. eggs (e) ; others fuses with one etc. 



sperm, (sp.) egg, forming 

 a zygote (z). 



