224 



THE SPOROZOA 



gametocyte produces four microgametes (Fig. 56). One of the latter 

 fertilises the ripe macrogamete, while the other three perish. 



Fio. 56. 



Conjugation of ' Addea ovata, A. Schu. (par. Lithobius forfleatus), after Siedlecki [55], slightly 

 modified, a, a microscliizont, not full-grown (compare Fig. 55, d), becomes a niicrogametocyte 

 ( <J ga'inc) and attaches itself to a macroschizont or macrogametocyte ( 9 game), b, the nucleus 

 of the microgametocyte divides c, into four daughter nuclei, which become d, four microgamtes 

 ( (J gam). The karyosome of the microgametocyte disappeared when division of the nucleus 

 commenced, e, one of the microgametes penetrates the macrogamete, which forms a fertilisa- 

 tion-spindle, composed of c$ and ? chro matin (chr), still distinct from each other, and occupy- 

 ing opposite poles of the spindle. The other three microgametes ( <$ gam), and the residual 

 protoplasm of the microgametocyte (r.p), containing the pigment granules, perish and dis- 

 integrate on the outside of the macrogamete. The karyosome of the macrogamete has broken 

 up, and disappeared as such. /, the complete union of the chromatin from the two sources 

 produces the single nucleus of the zygote (n.zyg). 



Note. In this conjugation an apparent difference in the stages is caused by the position of the 

 nucleus of the $ gamete, which places itself at one pole of the body, either at the pole nearest 

 to the microgametocyte (a, c, e) or at the pole furthest from it (b, d,f). In the first case the 

 fertilising microgarnete penetrates the microgamete at once, and the three residuary micro- 

 gametes are formed near the remains of the microgametocyte. In the second case all four 

 microgametes travel round to the pole furthest from the microgametocyte, where penetration 

 of the fertilising element takes place (/). 



In A. mesnili and Eimeria nova the development is similar, but 

 the gametocytes may or may not associate before the maturity of 



