244 



BIOLOGY OF THE PROTOZOA 



bud (pansoproblast) 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 

 degenerate 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. 186, p. 447). Of the 6 nuclei in each 

 cell, 2 are "somatic" and take part in the formation of the shell or 

 capsule 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 





Fig. 121. — Grtgarina cuneata. A, surface view of sporocyst with ripe sporoblasts 

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

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



nuclei which, according to observations of several different authori- 

 ties, later fuse into one (p. 547). 



In all of these cases the specialized structures accompanying 

 spore formation are formed only at one period in the life cycle and 

 a period which comes at the end of long-continued metabolic activ- 

 ity. They represent therefore, a differentiated protoplasm which is 

 not evident in the protoplasmic make-up of the progeny. What 

 is true of these visible differentiations is also probably true of 

 analogous differentiations which are not visible, and we have reason 

 to l)elieve that the products of unequal division and of multiple 

 division are not encumbered by protoplasmic conditions which 

 hamper vitality— in other words, that they have undergone rejuven- 



