6o6 PATTERNS AND PROBLEMS OF DEVELOPMENT 



Gamete formation in the gregarines commonly takes place in a cyst 

 containing two individuals. In each of these nuclear multiplication, some- 

 times to a great number, occurs, each individual in such cases becoming 

 an irregular mass with extensive surface. The nuclei become superficial, 

 and a gamete forms about each nucleus, one of the original individuals 

 giving rise to microgametes, the other to macrogametes. Figure 189 shows 

 a stage in formation of macrogametes (A) and microgametes (B) in a 

 eugregarine. Superficial nuclear position apparently results from reaction 

 to a surface-interior differential in the mass, and the outgrowth in rela- 

 tion to each nucleus is again a budding of cells from the common mass, 

 apparently initiated either by the nucleus or by cytoplasmic factors closely 

 associated with it, such as may be indicated morphologically by a centro- 

 some or blepharoplast. 



A B 



Fig. 189, A, B. — Stage in gamete development of a gregarine, Urospora lagidis. A, mega- 

 gametes; B, microgametes (after Brasil, 1905). 



Cell formation by budding from a multinucleate mass in relation to a 

 nucleus is very generally characteristic not only of gregarines but also of 

 Coccidia and Haemosporidia, and not only in development of merozoites 

 and sporozoites but in that of gametes. A stage in development of micro- 

 gametes of a coccidian is outlined in Figure 190, A. The fully developed 

 microgamete is a greatly elongated, filamentous, biflagellate cell with 

 undulating membrane and nucleus also elongated to filamentous form. 

 The polarity arising in the bud which gives rise to this filamentous cell 

 apparently determines its axiate pattern. Developmental stages of the 

 microgamete of the tertian-fever parasite, a haemosporidian, indicated 

 in Figure 1 90, 5, show a similar cell-budding in relation to nuclear position ; 

 microgametes of other Haemosporidia develop similarly. In general, re- 

 action to a surface-interior differential and a local budding of cells from 

 a multinucleate mass are apparently concerned in origin of such axiate 

 pattern as these forms possess. 



