566 MAYOR. 



separate chromatin granules are not to be distinguished. The two 

 germ-nuclei remain unaltered. 



In spores which have been for some time in sea water or in the 

 stomach of another host, the nuclei of the valve-cells are no longer 

 to be seen and the nuclei of the capsulogenous cells appear as small 

 deeply staining masses near the polar capsules. The nuclei of the 

 capsulogenous cells in the fully formed spore are described by The- 

 lohan ('95), Doflein ('98), Plehn (:04), Schroder (:07), and others, as 

 small deeply staining bodies adherent to the polar capsules. 



C. Structure of the Fully Formed Spore. 



In studying the structure of the spore it is convenient to use the 

 method of orientation employed by Thelohan ('95, p. 250-251) and 

 generally adopted by subsequent writers. Where there is a single 

 polar capsule (cps. poL), or two (Fig. A), or more, close together, the 

 part of the spore in which the capsules lie is called anterior (a in Fig. A). 

 The plane, a., p. (Fig. A), passing through the suture separating the 

 two valves, is called the sutural plane. The spore is oriented by 

 placing it with the polar capsules in front, and the sutural plane 

 vertically (Fig. A). Then the front is anterior (a. Fig. A), the upper 

 surface dorsal, and the lower surface ventral, the right side the right, 

 and the left side the left. The sutural diameter (Thelohan, '95, p. 

 251) is the greatest diameter in the sutural plane. The bivalve axis 

 (dx., s., Fig. A) is the line w^iich measures the greatest distance be- 

 tween the two valves, perpendicular to the sutural plane. 



The general shape of the spore of Ceratomyxa acadiensis, may be 

 described as that of a spindle of which the longitudinal axis has been 

 bent into the arc of a circle. The chord of this arc is the bivalve axis, 

 and may be called the width of the spore. The convex side of the 

 arc is anterior, the concave side, posterior. The sutural axis extends 

 in the antero-posterior direction and is equivalent to the length of 

 the spore. The two valves are cone-shaped, the pointed ends being 

 directed one to the right and the other to the left, and the bases meet 

 along the plane of suture. The spore is slightly compressed dorso- 

 ventrally. A slight variation in the foim and dimensions of the 

 opposite valves was often noticed. This was not, however, constant, 

 nor was it sufficient to show the degree of asymmetry found by 

 Doflein ('98, p. 284) in such spores as those of C. inaequalis Doflein. 

 The lateral filaments extending outwards from the tips of the valves 



