THE SPOROZOA 



153 



about a central residual mass, lie in the centre, the unused portion 

 of the original protoplasm forming a thick layer about them. At 

 the same time, a third and very delicate membrane, probably com- 

 posed of the residual peripheral mass, is formed inside of the cyst 

 and against the second or inner coating. Six to eight radial thicken- 

 ings can be seen later in this residual portion, and each of these 

 develops a distinct lumen, thus becoming tubular and extending 

 through the residual mass of protoplasm to the new internal mem- 

 brane. Each tube expands at the extremity into a disc-like cup, while 

 the inner part of the tube is lost in the central mass of spores. In 

 * some unexplained way the walls of the primary cyst open, leaving the 

 protoplasm and the spores 

 inclosed only by the third 

 membrane. The tubes 

 already formed then evag- 

 inate, and the cylindrical 

 portion of the tube is 

 thrown to the outside. 

 The tubes act as spore- 

 ducts for the inner archi- 

 spores, each of which 

 contains the definite num- 

 ber of sporozoites (Fig. 



S 



Fig. 85. Spore-ducts of Gamocystis tenax. 



SCHNEIDER.] 



d, spore ducts; s, spores in an external gelatinous 

 mantle. 



Sporulation of the Coc- 

 cidiida is strikingly similar 

 to that of the Gregarinida. 

 Here, as a rule, only one 

 membrane (capsule) is 

 formed around the spheri- 

 cal animal ; and the nu- 

 cleus, in addition to 



division through mitosis, frequently fragments into as many pieces as 

 there are to be archispores (fragmentation). Before the nucleus divides, 

 a certain amount of the chromatin is given off, as in the Gregarinida, 

 to form what Labbe calls the equivalent of the " polar body " of 

 the Metazoa. Again, as in the Gregarinida, the archispores or sporo- 

 cysts are arranged around the periphery, and a residual mass occu- 

 pies the centre. The archispores which are liberated by simple rupture 

 of the walls of the cyst, form a definite number of sporozoites, varying 

 from one (monozoic) or two (disoic) to many (polyzoic\ In some forms 

 of Coccidiida either sporozoites or archispores may be formed directly. 

 The number of spores formed is usually small, as in Coccidium, where 

 the nucleus divides only twice, producing only four archispores, each 



