THE SPOROZOA 167 



containing paraglycogen granules and a few abortive nuclei, 

 and there is no longer any trace of the individual gametocytes. 

 The gametes now begin to move actively in the cystic fluid ; 

 how their movements are affected is not accurately known, 

 but after a time they become slower, and then the gametes 

 unite together in pairs and conjugate (fig. 35, }. First the 

 cell bodies of each pair fuse together, then their nuclei ; but 

 the latter do not form a mitotic figure and the chromatin 

 granules derived from the two gametes do not fuse, but are 

 simply mingled together in the conjugation nucleus.' It is 

 not certain, but is very probable, that the gametes derived 

 from one of the associated gametocytes conjugate with those 

 derived from the other gametocyte, and this view is strengthened 

 by the fact that in an allied gregarine, Lankesteria ascidice 

 parasitic in the alimentary canal of the sea-squirt Ciona inles- 

 tinalis, a similar association of two gametocytes and production 

 of gametes has been observed. In one instance one of the 

 gametocytes perished within the cyst, while the other proceeded 

 on its normal course of development and gave rise to a crop 

 of gametes, but these exhibited no affinity for one another, 

 did not conjugate, and eventually perished for want of partners 

 derived from another individual. The individuals formed by 

 the conjugation are the definitive sporoblasts or zygotes : they 

 are of course half as many in number, but each of them is 

 nearly twice as big as the original gametes. They are then, 

 while still contained in the cyst, transformed into spores in the 

 following manner. Each zygote becomes oval in shape and 

 secretes a substance resembling chitin from its surface, which 

 hardens to form a characteristic lemon-shaped spore coat or 

 sporocyst (fig. 35, C and D). Within this protective coat 

 the nucleus of the zygote undergoes three successive amitotic 

 divisions, giving rise to eight nuclei, arranged more or less in 

 the plane of the equator of the spore. A portion of the proto- 

 plasm of the zygote is then segmented off round each nucleus, 

 and thus eight minute curved bodies are produced, arranged 

 round a core of residual protoplasm, much as the divisions 

 of an orange are arranged round its central fibrous axis 

 (fig- 35 &) During the formation of the spores the cystic 

 residuum is slowly absorbed, and the spherical cyst originally 

 formed by the associated gametocytes contains nothing but a 

 great number of spores which, from their resemblance to the 



