SMALLWOOD : MATURATION OF HAMINEA SOLITARIA. 277 



centrosome ; the centriole (c'l.) gradually becomes indefiuite in outline 

 and decreases in size until (Figs. 25-28, Plate 5) one is unable to 

 recognize it. The extent and form of the centroplasm (c'pl.) at its 

 maximum development are best illustrated in Figure 21 (Plate 4), 

 which is from a section somewhat oblique to the long axis of the spindle, 

 so that the centroplasm appears larger than it would have done had the 

 section been perpendicular to this axis. This is the largest centroplas- 

 mic body that has come under my observation ; its margin is very 

 irregular and conspicuously crenate, being drawn out in the direction 

 of the more conspicuous astral rays. The crenate condition of the 

 centroplasm is characteristic of this stage. Later it becomes even in 

 outline (Figs. 25, 28). 



Figure 25 (Plate 5) shows, at the inner pole of the spindle, a condition 

 ■which I believe to be one of the phases through which the centrosome 

 regularly passes : there is in this case no single body which we may 

 describe as a centriole ; however, there are to be distinguished in the 

 centroplasm a number of very minute granules, which take a basic stain, 

 and have a tendency to collect near the middle of the centroplasm. 

 Figure 28 illustrates a similar condition. The stages represented in the 

 two figures show that these gi'anules have a slight tendency to an 

 arrangement parallel to the axis of the spindle. In Figure 25 their 

 axis makes only a small angle with that of the spindle, and in Figure 

 28 (inner pole) it is practically parallel to that axis. However, there 

 is such a scattering of the granules that it is unsafe to attribute much 

 importance to their arrangement. Furthermore, it is sometimes (outer 

 pole of Figure 28) impossible to distinguish any granules in the centro- 

 some. These eggs all show good fixation, and a satisfactory preservation 

 of all the parts. At the outer pole of Figure 25 the granules are 

 represented by a single body, — a typical centriole. This condition has 

 been observed in a large number of eggs taken from different animals 

 and treated with various stains. Boveri (:0l) believes that the scattered 

 condition of the centriole substance is due to poor fixation. Had this 

 condition been observed in the eggs from only one or a few animals, I 

 should hesitate to disagree with his interpretation ; still, it seems as if 

 Boveri were strangely inconsistent, for when he comes to describe a 

 similar stage in the eggs of Echinus microtuberculatus, he shows (Taf. III. 

 Fig. 27-31) that there are a number of minute particles distributed in 

 the centro[)lasm, and that these particles gradually become less distinct 

 until they almost disappear. In the next stage in Echinus these small 

 granules have become a narrow band in tiie centroplasm, each end of 



