AN INTRODUCTION TO ZOOLOGY 



E. A more complex colony of cells (Volvox). 



CELL DIVISION CELL DIVISION CELL DIVISION PERMANENT CELL DIVISION 

 (Colony for- (Asexual Re- (Gamete for- CONJUGATION (Colony for- 

 mation) production) mation) (Fertilization) mation) 

 Zygote (2) Germ cells (g.c.) Certain germ One sperm Zygote develops 

 develops into a give rise to cells produce fuses with one into a colony. 

 colony. new colonies, eggs(e); others egg, forming a 

 spermatozoa zygote (z). 



F. A simple Metazoon (Hydra). 



CELL DIVISION 

 ( Embryological 

 development) 

 Zygote (z) pro- 

 duces animal 



containing 



germ cells (g.c.) 



and two layers 



of specialized 



somatic cells, the 



ectoderm (ec.) 



and entoderm 



(*). 



BUDDING CELL DIVISION PERMANENT CELL DIVISION 

 (Asexual (Gamete for- CONJUGATION (Embryological 

 Reproduction) mation) (Fertilization) development) 

 Part of animal Certain germ One sperm Zygote (z) pro- 

 separates from cells produce uniteswith one duces animal, 



parent and one egg (e) and egg, forming a etc. 



leads separate two polar zygote (z). 



existence. bodies (ph.); 

 others produce 

 many sperms 



