746 MUKIEJ. IJOUEKTSON. 



somes and certain amoebse. I am inclined to tliink that it is 

 simply formed by the running together of the grains of 

 chromatin. Forms are sometimes found in the blood of the 

 tortoise which show the chromatin arranged in an inner and 

 outer ring ; this type is sliovvn in fig. 5. Finally', forms are 

 also seen in which the chromatin is in the shape of a large 

 number of irregularly disposed granules, which may at times 

 give the appearance of a kind of reticulum (figs. 6, 17, and 

 18). In H . nicoriae, as in almost all the species known, there 

 are, in addition to the young forms, two types in the blood of 

 the vertebrate host, the one a bean-shaped organism with an 

 approximately central nucleus, the other a long recurved 

 creature with its nucleus situated in the broader limb near 

 the bend (see figs. 1, 3, 8, 9, 17 and 18). The bean- 

 shaped form is always present in far greater numbers than 

 the fully developed vermiform individuals, but specimens are 

 very common Avhere the more slender recurved limb is only 

 about half as long as the broad limb (figs. 2 and 9a). This is 

 one of the points in which the wet fixation method is so much 

 superior to the dried films. In the latter the great majority 

 of these specimens, where the recurved limb is shorter than 

 the broad one, appear simply to be bean-shaped, the drying 

 having artificially obscured the recurved limb. There are no 

 very marked or constant nuclear differences in these tj'pes ; 

 it may, however, be observed that generally speaking the 

 larger bean-shaped forms show the more scattered arrangement 

 of the chromatin. The smaller bean-shaped individuals and 

 the half recurved creatures have usually the more symmetrical 

 circular type of nucleus, while the large vermiform specimens 

 have a slightlj^ elongated nucleus, with a tendency for the 

 chromatin masses to run together at their edge. A glance 

 at the figures will make these points clear. 



Two main theories as to the significance of the beau-shaped 

 and vermiform (fully recurved) creatures have been put 

 forward : (1) That the bean-shaped individuals are macro- 

 gametes or macrogametocytes, and the recurved ones micro- 

 gametes or microganietocytes. These two different types or 



