240 



BIOLOGY OF THE PROTOZOA 



of the cyst. These are formed from residual "chromidia" which 

 collect in rings about the periphery and from which the finger- 

 formed tubes grow into the mass of developing zygotes (Fig. 125). 



When the cysts are mature absorption of water causes the rupture 

 of the cyst walls, the tubes are forced out and evaginated as an 

 inturned glove finger may be blown out. The spores then are 

 distributed through these hollow tubes or sporoducts. 



In Myxosporidia still more complicated structures recalling the 

 capillitia of Mycetozoa, are characteristic of the spore-forming 

 stages. In Syhaeromyxa sabrazesi according to Schroder (1907) and 

 in Myxobolus pfeifferi according to Keysselitz (1908) the internal 



Fig. 125. — Gregarina cuneata. A, surface view of sporocyst with ripe sporoblasts 

 issuing from sporoducts (e). B, C, sections of sporocyst with ripening spores and 

 developing sporoduct (0- (From Calkins after Kuschakewitsch.) 



bud (pansporoblast) which is destined to form the spores, contains 

 two nuclei, one of which is smaller than the other. These nuclei 

 increase by division until there are 14 altogether; 2 of these degen- 

 erate without further function, and the remaining 12 are divided 

 into two groups of 6 each, the protoplasm dividing with them to 

 form two protoplasmic multinucleated bodies which will develop 

 into sporoblasts (Fig. 164, p. 325). Of the 6 nuclei in each cell, 

 2 are "somatic" and take part in the formation of the shell or cap- 

 sule of the sporoblast; 2 others are also "somatic" and participate 

 in the formation of the polar capsules and threads characteristic 

 of the Cnidosporidia; the remaining 2 nuclei persist as germinal 



