THE SPOROZOA 



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neighbouring cells. The Gregarine meanwhile is also increasing 

 in size, and its rate of growth exceeds that of the infected cell. 

 When it is large enough to fill the hypertrophied host -cell, 

 degeneration of the latter commences (Fig. 10, b). Its nucleus 

 shrinks, becomes crescent-shaped, and finally becomes a flattened 

 corpuscle which stains strongly and consists of debris of chromatin. 

 At the same time the cytoplasm is absorbed until it forms a thin 

 skin enclosing the Gregarine, and is finally cast off with it from 

 the epithelium. It is remarkable that in other cases a similar 

 series of changes may be provoked in the epithelial cell after the 



Fio. 10. 



Intracellular stages of Lankesteria ascidiae (Lank.) (par. Ciona intestinalis) in the intestinal 

 epithelium, a, young stages showing the hypertrophy of the epithelial cells induced by the 

 parasites at an early stage. 6, older stage showing very great hypertrophy of the epithelial cell, 

 with atrophy of its nucleus, ep, normal epithelial cell ; ep', hypertrophied epithelial cell con- 

 taining (G) the young Gregarine : n, nucleus of normal cell ; n', nucleus of infected cell. (After 

 Siedlecki, x 750.) 



Gregarine has grown out from it, and is attached to the cell only 

 by a minute point of contact (Fig. 11). 



In many cases a Gregarine, after having been set free from an 

 epithelial cell which it has destroyed, may secondarily attach itself 

 again to the epithelium (Figg. 12 and 13). Although such second- 

 ary attachment may be exceedingly complicated, and may affect a 

 large number of epithelial cells, as in Pterocephalus (Fig. 12), never- 

 theless it only produces mechanical alterations in the cells, and never 

 has the marked effects which result from the primary attachment. 



It is thus seen that the Gregarine destroys completely the cell in 

 which it is parasitic at the commencement of its career. Never- 

 theless Gregarines appear to be extremely innocuous to their hosts. 

 Since they do not reproduce themselves by schizogony, except in 

 a very few instances, they do not overrun their host in the way 



