16 PROCEEDINGS OF THE ACADEMY OF [Jan., 



the cell contours are sharp and a periplast can be seen. The nucleus, 

 however, shows merely as a faintly stained vacuole containing some 

 formed substance, the details of which could not be made out. It 

 may here be remarked that in most of the cell parasites the nucleus 

 appears as a vesicle containing a nuclear net, and that in general 

 this nuclear net is the only part of the nucleus that stains. Hence 

 the net appears as though projected against a clear background. 

 On the other hand, it is frequently to be observed in the spores free 

 in the lumen, and much less frequently in those in the cells, that the 

 nuclear sap as well as the nuclear net has taken the stain, thus 

 obscuring the details of the latter. This condition is illustrated by 

 %. 6. 



In the preliminary note it was stated that at least a portion of the 

 intracellular spores rapidly underwent a change which expressed 

 itself in a reduction of the cytoplasm and an increase in the size of 

 the nucleus, the ultimate result of which was the production of a 

 body which was apparently only the enlarged original nucleus, the 

 cytoplasm having apparently all disappeared. This, it was stated, 

 was interpreted to be the male form. 



This evolution is illustrated in Plate I, figs. 7 to 11. Fig. 7 shows the 

 nuclear enlargement with no great amount of cytoplasmic reduction. 

 The nucleus is large and turgid, it causes the sides of the parasite to 

 bulge and shows a distinct net. This net consists of a central aggre- 

 gation from which strands run to the periphery. As already indicated 

 in the discussion of figs. 3 and 4, whereas the appearance of this 

 central aggregation differs considerably in the different specimens, 

 its structure appears to be fundamentally the same throughout. It 

 seems to lie merely the close-meshed central part of the nuclear net, 

 with the interspaces sometimes empty and sometimes filled in with 

 faintly staining chromatin. The latter is the more primitive 

 condition. 



The parasite shown in fig. 7 was from int. 15, or about the middle 

 of the intestine, and hence is presumably that of a parasite which 

 has been within the cell for some little time. Except, however, for 

 the notable enlargement of the nucleus, it has all the characteristics 

 of a very early stage. 



Fig. 8, from int. 30, represents a condition in which there has been 

 as yet no great amount of nuclear enlargement, but a slight degree of 

 cytoplasmic degeneration. In fig. 9 there is shown nuclear enlarge- 

 ment accompanied by a consiclerable degree of cytoplasmic degenera- 

 tion, as is evidenced by the vacuolization and rough contours of the 



