20 CALIFORNIA ACADEMY OF SCIENCES. [ 3 d Ser, 



wanting the microcentrum, in which case it cannot of course 

 lay claim to the name of plasmocytoblast. In the upper 

 one we have no difficulty in recognizing the outer plasmo- 

 sphere with its fringed margin. The transparent hyalo- 

 sphere comes next to it, almost or entirely unstained. 

 The granosphere, which is very large, is stained violet, 

 while the centrosphere is stained even deeper, rather 

 an exception to the rule. Lowest down at the base are seen 

 the somospheres, containing several dark spots, or centro- 

 somes. 



The other type of plasmocytoblast, represented by dia- 

 gram 2, is the one that is seen in figs. 32$, etc. We find 

 that the centrosphere with its enclosures has traveled away 

 from the nucleus and the base of the cone towards its 

 apex, much more so at b than at a. In fig. 35 we find 

 that at the pole b the spheres are arranged according to the 

 conelike type, while at the pole a the spheres have assumed 

 the final spherical shape, the granosphere surrounding the 

 archosome about equally on all sides. The variation 

 between these two extreme types of plasmocytoblasts is 

 such that we seldom find two which are exactly alike, still, 

 the similarity is sufficiently great to allow us without diffi- 

 culty to recognize each respective zone. We will now con- 

 sider these spheres more in detail, beginning with the outer 

 one, or plasmosphere. 



VII. Cytosome. 



The Plasmosphere. — This, the most exterior sphere of 

 cytoplasm, is especially developed at the poles, where its 

 tendency to assume amoeboid projections is very noticeable. 

 MacCallum and Griesbach have previously described the 

 poles of the fusiform corpuscles as being frayed. The in- 

 creased size of the plasmosphere at the poles may be seen 

 in figs. 32, 33, 34, 35, etc. The plasmosphere may be 

 much larger at one pole of the fusiform corpuscle than at 

 the other, and this inequality in size is also correspondingly 

 shared by the other spheres. In other words, the spheres 



