564 MAYOR. 



has both its ends on the same side of the other sporoblast (PI. II, 

 Figs. 38, 39); but their bivalve axes may make an angle with each 

 other, so that the two ends of one sporoblast are on opposite sides of 

 the other sporoblast. This close contact of the sporoblasts is con- 

 tinued throughout their later development, and even the fully formed 

 spores found floating in the bile are usually associated in pairs, and in 

 the same relative position as that described for their sporoblasts. In 

 each of the sporoblasts one of the polar capsules has reached a more 

 advanced stage than the other (PI. II, Figs. 31, 34), for while one 

 preserves the condition of the previous stage, the other appears as a 

 deeply stained spherical mass, having retained the stain owing to its 

 thicker membrane. This inequality in the rate of development of 

 the two polar capsules of the same spore seems to be of frequent occur- 

 rence in this species, a fact which would indicate an independent action 

 on the part of the two capsulogenous cells. The nuclei of the sporo- 

 plasm — the germ-nuclei — lie close together in the sporoplasm and are 

 so arranged that the nuclei in one sporoblast lie in the end diagonally 

 opposite to the end in which the germ-nuclei of the other sporoblast 

 lie (PI. II, Fig. 38). This relation of the nuclei of the sporoplasm of a 

 pair of sporoblasts is the one usually found, but other arrangements 

 occur; e. g., the nuclei of the sporoblasts may lie in the corresponding 

 ends of their sporoblasts or one pair may lie in the middle of its 

 sporoblast while the other pair lies nearer one end of its sporoblast. 

 The latter condition is realized in Figure 39 (PI. II), where the nuclei 

 of the sporoplasm in the left sporoblast, not drawn in the Figure, lie 

 in the middle of the sporoblast, and so that a line joining their centres 

 would correspond very nearly to the antero-posterior axis of the sporo- 

 blast, whereas in the right sporoblast the germ-nuclei occupy the half 

 of the sporoblast which is below in the figure. Other cases were found 

 where the nuclei of one sporoblast were far apart and in opposite 

 halves of their sporoblast (PL II, Fig. 35), while those of the other 

 pair were near together in the same half. A myxosporidium con- 

 taining a pair of sporoblasts in a still later stage of their development 

 into spores is represented in Figure 38 (PI. II). The nuclei of the 

 sporoblasts are represented diagrammatically by circles, those at a 

 deeper focus being indicated by a paler line. In the sporoblasts 

 (PI. II, Figs. 37, 36) the nuclei of the valve-cells show the chromatin 

 granules collected in clumps at the periphery of the nucleus, which 

 has a clear interior. The nuclei of the capsulogenous cells show a 

 similar condition in a slightly less advanced state. The structure of 

 the germ-nuclei is as before. The pairs of these nuclei, however, 



