MEIOSIS 



251 



quartet of spermatids, which then transform into spermatozoa (p. 214). 

 In the female they result in an egg and three (sometimes only two) 

 polocytes (p. 213). Each gamete, male or female, thus contains the 

 reduced, or gametic, number of chromosomes. In bryophytes and 

 vascular plants meiosis occurs normally during sporogenesis, hence the 

 spores are formed in quartets. Each spore carries the reduced number of 

 chromosomes, this number being retained through the development of the 

 gametophyte and its gametes (p. 204). The conditions found in lower 

 plants will be summarized toward the end of the chapter. 





ANIMAL 





Fig. 148. — Diagram of chromosome cycles of animals and plants. 



The term meiocyte may be used to designate any cell in which meiosis is 

 initiated, whatever its origin or position in the life cycle. ^ In higher 

 animals the meiocytes are therefore the primary spermatocytes in the 

 male and the primary oocytes in the female. In bryophytes and vascular 

 plants they are the sporocytes — the microsporocytes and megasporocytes 

 in heterosporous forms. The immediate products of meiosis, i.e., the 

 nuclei or cells formed in quartets, may be referred to as gones. 



Preliminary Sketch of Meiosis. — Before proceeding with the detailed 

 description of meiosis it will be advantageous to have clearly in mind 

 certain general features of the process without the complications which 

 must be introduced later, and to visualize the more conspicuous differ- 



^ Other terms which have been used in this sense are auxocyte (Lee, 1897) and 

 gonotokont (Lotsy, 1904). 



