1910.] MORPHOLOGY OP EIMERIA AVIUM. G81 



towards the raacroganietes. Tlie niicrogametes svvnrm round tlie 

 micropyle of the macrogainete (PI. LVII. fig. 47 * ) and several have 

 been seen trying to enter it simultaneously. The nucleus of the 

 macrogamete travels upwards nearer the micropyle, and before 

 long, one microgamete effects an entiy (fig. 47 *), appears to bore 

 its way into the female, reach the nucleus and fiually be lost to 

 view. The macrogamete seci'etes a plug of protoplasm aci-oss the 

 micropyle, whereby other microgametes are excluded, and the 

 individuals thus shut out degenerate (fig. 48). Such is the pi'ocess 

 of conjugation as seen in the living oi'ganism, and the evidence 

 of stained prepai-ations is fully confirmator}^ of what has jvist 

 been desci-ibed. 



Owing to the presence of granules in the macrogamete it is 

 extremely difficult to follow the subsequent stages of fertilisation. 

 Occasionally there are indications of a fertilisation spindle 

 (figs. 50, 51), but the nature of the material frequently precluded 

 observation of the same. 



The term "fertilisation spindle" is not exactly a happy one, 

 for the object of that structure is the intimate intermingling of 

 the chromatin of the uniting gametes. 



(e) S'j^oroyony. 



After the microgamete has reached the nucleus of the macro- 

 gamete, fusion occurs and a zygote is produced. The contents of 

 the zygote at first fill the oval oocyst (PI. LVII. figs. 49-52) but 

 gradually they shrink away from the poles t. The oocyst itself 

 may increase slightly in size during the concentration of its 

 contents, which ultimately form a globular mass, consisting of 

 cytoplasm rich in fatty matters, within which is a nucleus, usually 

 centrally placed. 



The nucleus of the zygote pi'oceeds to divide directly first into 

 two (figs. 53, 56) and then into four (fig. 54), the divisions follow- 

 ing one another very rapidly. The granular protoplasm segments 

 around the nuclei, and four sporoblasts (fig. 57) are produced, 

 each sporoblast sepaiuting from its neighbours as a small, rounded 

 body (figs. 55-57). Occasionally oocysts containing two ovoid 

 masses of protoplasm (fig. 82) are seen, but as a rule the form 

 containing four sporoblasts is the one found, the four sporoblasts 

 being formed almost concurrently. The sporoblasts become ovoid 

 (PI. LVII. fig. 58 ; PI. LVIII. fig. 68) and each gradually secretes 

 a tough, chitinoid sporocyst, usually difterentiated as epispore and 

 endospore, and so becomes a firm, resistant spore (PI. LVIII. 

 figs. 71-76). A minute amount of the cytoplasm of the zygote is 

 not used in spore formation, but remains within the zygote as a 

 small cystal residuum. 



The sporocysts continue within the oocysts for some time, 



* See also PI. LXII. fig. 3 of my paper on Experimental Coccidiosis (this Journal). 

 t 111 some casei the zygo'e contents of the oocyst may be slightly nearer one pole 

 than the other. 



