682 uu. 11. n. iwxTUAM ox the [May 3, 



during wliicli peiiud each sporocy.st undergoes developuieutal 

 chaugt's, leading to the production of actively motile sporo- 

 zoite.s. Tlie contents of the spore at first are homogeneous 

 (PI. LYIII. figs. 68-70), but gradually two refractile Ijodies or 

 A-acuoles appear at either end {tig. 73), and the protoplasm 

 gradually concentrates into two masses, just internal to each 

 vacuole. The nucleus is at first centi'ai, l)ut divides into two, 

 and the halves migrate to the opposite poles of the sporocyst 

 (PI. LVII. fig. 58). The protoplasmic masses gradually displace 

 the polar vesicles, so that the two vacuoles move towards the 

 centre and coalesce (PI. LVIII. fig. 73), leaving nearly all the 

 protoplasm of the sporocyst in two masses, one at each end 

 (fig. 71). Each of the protoplasmic masses gradually becomes 

 vermiform, extending along one edge of the spore (figs. 71, 72). 

 Two vermiform sporozoites are thus formed (figs. 72, 74), some- 

 times with their more rounded ends placed at opposite ends of 

 the sporocyst (tete beche) (tigs. 72, 74, 75), sometimes with the 

 slightly swollen ends side by side (PI. LVII. fig. 59, PI. LVIII. 

 fio-. 76), the sporozoites being capable of movement within the 

 spore just previous to their escape. There is a slight sporal 

 residuum. 



The sporocysts when quite ripe tend to become more pointed 

 at one end \P1. LVII. fig. 60, PL LVIII. figs. 71, 75, 76), 

 where a slight thickening or small Stieda's plate (fig. 71) may 

 appear, which is a point of weakness, for here a rupture may 

 occur under the action of the digestive juices of the fresh host, 

 forming a sort of micropyle through which the sporozoites escape. 

 Partially ruptured sporocysts are sometimes found (PI. LVII. 

 figs. 59, 60). In the case of grouse chicks dying from acute 

 coccidiosis, ripe sporocysts have been found in the cascal walls 

 themselves, as well as in the ca?cal contents, though usually 

 mature sporocysts are found in cjecal droppings that have been 

 exposed. 



The oocysts of Eimeria av'mni show a fair amount of variation 

 among themselves. Usually the oocysts are oval (PI. LA'^III. 

 fit's. 65-68, 71, 72, 77, 78), actually measured specimens varying 

 from 25/jito 35 ytx, in length and from 14yLt to 20)u in breadth. 

 Sometimes the oocysts are not oval but subspherical (fig. 70), and 

 these are from 18 ^ to 20 /a in diameter. Somewhat pyriform or 

 egf-shaped oocysts (fig. 69) are intermediate in size between the 

 oval and subspherical forms. Morse (1908) noted the occurrence 

 of both round and oval oocysts when investigating white diarrh»ca 

 of f(jwls, in which coccidiosis played an important part. 



Anion"' the oocysts of K. avium certain were found with 

 somewhat squarish ends (fig. 78) while others had a sliglit 

 depression at the apex (fig. 79), but their development was 

 identical with that of the more connnou forms. Occasionally, 

 oocysts with two sporocysts only (figs. 81, 82) were foiuid. but 

 these were abnormal foiius. as was also a parasite (iig. 83) in 



