CORPUSCLES OF MARINE WORMS. 139 



diameter of *05 mm., or about three times the diameter 

 of the disc-shaped corpuscles. It consists of a single cell 

 of colourless protoplasm containing in its substance a 

 solid, refringent rod. The rod is exactly the shape of a 

 bow, thicker in the middle than at the tapering and 

 recurved tips. Over the ends and convex side the pro- 

 toplasm stretches in a thin layer. On the concave side 

 the body of the cell is placed, occupying the space between 

 what would be the line of the bow string and the rod 

 itself. The nucleus is placed close to the rod on its 

 concave side, and very often it lies to one side of the rod, 

 partially covered by it, or lying over it, according to the 

 side on which the corpuscle is lying in the preparation. 

 The nucleus stains with hematoxylin, but not deeply; it 

 is noticeable that the thin cap of protoplasm which covers 

 the tips of the rods also stains with haematoxylin. From 

 both convex and concave side filamentous processes of 

 protoplasm stretch out, which may be seen in fresh pre- 

 parations, slowly waving about backwards and forwards. 

 Those on the convex side may be all slightly curved, to 

 the same degree and in the same direction. The pro- 

 cesses, especially on the concave side, are often engaged 

 in toying with the disc-shaped corpuscles. With the 

 exception of a few vacuoles I have seen nothing else in 

 the protoplasm. 



The rod itself is of a pale yellow colour. It appears in 

 a few corpuscles which seem to be degenerating, to be 

 slightly out of shape ; and in small ones may be more bent 

 than in the larger. As a rule, however, it preserves an 

 uniform appearance like that of a strung bow. One can 

 sometimes see in it longitudinal striations. Viewed by 

 polarized light, it appears of a different colour to the rest 

 of the field, an indication that it is no optical appearance 

 only, but is, in fact, a structure. It is also noteworthy 



