2i8 THE SPOROZOA 



VI <? ). In the first place, they are more or less bean-shaped, and 

 only become spherical during the maturation stages. In the second 

 place, they are early marked out by the fact that from the youngest 

 stages of the trophozoite onwards, they store up in their cytoplasm 

 large quantities of reserve material in the form of the so-called plas- 

 tinoid granules, bodies varying in diameter from \ //, to 1 /z, and very 

 refringent, rendering the macrogametocytes whitish and opaque. 

 The protoplasm is coarsely alveolar, and contains also another kind 

 of granule less abundantly. The quantity of food-substance which 

 the macrogametocytes store up retards their development consider- 

 ably, so that they lag behind the male cells in this respect. 



The plastinoid granules are very characteristic of Coccidia, and consist 

 of a substance termed Coccidin by Labbe", which resembles, but is distinct 

 from, the granules of paraglycogen, pyxinin, etc., found in Gregarines. 

 The plastinoid granules are stained yellow by iodine (not wine-coloured, 

 like the paraglycogen granules), and retain this colour after treatment with 

 sulphuric acid ; they are not soluble in weak acids or alkalis, nor in ether, 

 chloroform, or alcohol. They are not stained by haematoxylin solutions, 

 nor by Heidenhain's Iron- Alum method, nor yet by picrocarmine or borax- 

 carmine ; they are evenly stained, like the protoplasm, by Eosin, Aurantia, 

 and Thionin ; and Rhumbler's Eosin-Methyl Green mixture tinges them 

 red. The other kind of granule mentioned above is distinguished by taking 

 haematoxylin stains, especially by Heidenhain's method. (See Schaudinn 

 [51], p. 250 ; Wasielewski [7], p. 51 ; and references.) 



Each macrogametocyte becomes a single macrogamete, and to 

 this end it goes through a process of maturation which has some 

 points of resemblance to the development of the microgametes, but 

 differs as widely as possible in detail (Fig. 5 1, VII 9 ). The schizogony 

 is completely suppressed, and maturation is effected simply by the 

 expulsion of the karyosome, which travels during the space of about 

 one hour from the centre to the periphery of the nucleus. It then 

 passes out into the cytoplasm, and there breaks up at once with ex- 

 plosive rapidity into numerous small fragments which are expelled 

 from the cell-body. During these events the macroyamete changes its 

 bean-shaped form by slow contraction into a spherical one, the entire 

 process lasting about two hours. Schaudinn suggests that it is the 

 plastinoid granules which by their pressure during the changes of 

 body-form squeeze out the fragments of the karyosome from the 

 cytoplasm, as a cherry-stone can be squeezed out of a cherry. The 

 contractions of the body have also the further effect of setting free 

 the macrogamete from the shrivelled host-cell, so that it now lies 

 free in the lumen of the gut of the host. The mature macrogamete 

 is a spherical cell with a large spherical pronucleus, as it may now be 

 termed, containing chromatin- granules but no karyosome. It is 

 now ripe for fertilisation, and is attractive to the microgametes, 

 many of which swarm round the macrogamete, but only one effects 



