1910.] 



MOKPlIOLOaY OF EIMERIA AVII'M. 



(iSS 



readied to the ability of the host to provide nourishment and to 

 the multiplicative powers of the parasite, and this results in tlie 

 onset of sexual diflereiitiation. (iameto,i^ouy may occur both in 

 the duodenum and cfecum. 



Certain schizonts become coiisidei'ably modified in one of two 

 directions. In the first case, food-material accumulates, and a 

 large, uninucleate food-laden form is produced (figs. 26-30). 

 This is the macroga.metocyte (text-fig. (55, 1 $ ), destined to give 

 rise to a single macrogamete (text-fig. 65, J 2 ). In the second 

 instiince (text-fig. 65, Id), nuclear multiplication of a finely 

 granular parasite (PL LVII. fig. 37) occurs, and the many 

 minute nuclei j)i"oduced reach the pei-ipheiy of the liast-cell 

 (figs. 38-42), and ultimately the now multinucleate microganieto- 

 cyte (text-fig. 65, J J ) gives rise to a large number of small, 

 motile microgametes (tigs. 43-46 ; text-fig. 65, K J' ). The macro- 

 gamete early on invests itself with a cyst-wall (figs. 35, 36) in 

 which a thin part or micropyle is left for the entry of the micro- 

 gamete (figs, 47, 48 ; text-fig. 65, K $ ). This oOc^'st-wall is 

 formed while the parasite is within the epithelium. 



Fertilisation (figs. 47, 48 ; text-fig. 65, L) occurs — the process 



Explanation of Text-fig. 65 continued (see opposite). 



I.-^ 



Ci. Merozoites arnuiged "en barillet," | M 

 al)out to issue from host cell. At 

 one end of tlio cluster residual proto- 

 plasm is seen. 

 H. Free merozoites, each with a small 

 karyosome. N. 



f 9 • Yoimg macrogametocy te with 

 chromatoid granules. 

 (? . Young microgametocy te with 

 [^ tine granulations. 0. 



f $ . Macrogamete with round nucleus 

 and chromatoid granules dis- 

 tributed through the cyto- 

 l)lasm. 

 J. -J (J. Microgametocyte with nucleus 



divided to form a large imniher P. 

 of bent rod-like portions, the Q. 

 future microgametes. Remains 

 l^ of karyosome seen m centre. 

 I "^ . Macrogamete showing plastinoid 

 granules, the chromatoid gran- 

 ules being largely used up in 

 forming the wall with which the 

 r.iacrogau\ete has invested itself, 

 the remaining chromatoid gran- 

 ules being arranged between the 

 plastinoid gian\iles. 

 (J. Microgametocyte with many bi- 

 rtagellate microgametes about to 

 separate from it. Karyosome 

 1^ left at the centre. 

 L. Fertilisation. One microgamete is T. 

 penetrating the macrogamete, while 

 other male cells are near the micro- 

 pyle but will be excluded. 



Proo. Zool. ,Sor. — 1910. Xo. XLT 



K.-^ 



Fertilisation. The male pronucleus 

 which entered through a micropyle is 

 hing above the female chromatin. 

 Degenerating microgametes are 

 shown outside the oocyst. 

 Oocyst (encysted zygote) with proto- 

 plasmic contents tilling it completely. 

 Nucleus with signs of fertilisation 

 spindle. 



Oocyst with contents concentrated, 

 forming a central, spherical mass 

 which has a vacuole in the middle 

 and the nucleus to one side. Many 

 such cysts seen in iid'ected ca'cjil 

 droppings. 



Oocyst with four nuclei. 



Oocyst with contents segmented to 

 form four rounded s])()robl;i,sts (as 

 seen in fresh prepariitioiis). 



Oocyst with four sporoblasts wliich 

 have grown oval and are becoming 

 sporocysts; the small cystal residuum 

 seen to one side. 



Oocyst with four sporocysts in each 

 of wliich two sporozoites are dif- 

 ferentiated. The oocyst in tliis 

 condition ultimately o])ens. liberatin? 

 the sporocysts, the ujjper one of 

 which is seen about to issue from the 

 oocyst. Slight crystal residuum. 

 fSporal residuum in each sporocyst. 



Sporocyst which has issued from 

 oocyst. Two sporozoites are within 

 it and have assumed the jiosition 

 most snittible for emergence. 



45 



