26 CALIFORNIA ACADEMY OF SCIENCES. [ 3 d Ser., 



having spread out to such an extent as to enclose one half 

 of the nucleus. In fig. 28 we see a plasmocytoblast with 

 three centrospheres in different stages of development, one 

 of which, having separated itself almost completely from the 

 vicinity of the nucleus, and carrying with it an envelope of 

 granosphere and centrosomes, is apparently ready to form an 

 independent plasmocyte. In the plasmocytes the centro- 

 sphere frequently assumes a large size and becomes more 

 differentiated, evidently a direct effect of development and 

 growth. In fig. 49, which represents a free plasmocyte, 

 the centrosphere is beautifully differentiated, having as- 

 sumed a deep pink eosin stain. In fig. 38a the centrosphere 

 is very large and rounded, pale blue, and surrounded by a 

 narrow rim of granosphere. The centrosphere frequently 

 assumes a star-shaped or irregular form, which indicates that 

 it possesses independent amoeboid movements. 



Somosphere and Centrosomes. — The innermost of the 

 spheres, which incloses one or more centrosomes, I have 

 named somosphere. I have not, however, been able in 

 every instance to demonstrate the presence of this sphere; 

 but in many, perhaps in the majority of corpuscles observed, 

 this sphere is distinct from the centrosomes. The dark 

 granules, or centrosomes, accepting this name as Heidenhain 

 understands it, are nearly always surrounded by this special 

 sphere, which generally stains darker than the centrosphere, 

 but sometimes also appears much lighter. It varies much 

 in size and form, but is less regular than any of the 

 other spheres, and undoubtedly possesses amoeboid activity. 

 In fig. 21 the somosphere is well marked, and in its center 

 are distinctly seen the darker granules, or centrosomes. It 

 would be incorrect to state that the centrosphere always en- 

 closes the somosphere, because frequently the latter is seen to 

 lie at one edge of the centrosphere, as represented in fig. 

 34a; or it may be even entirely separate from it, though this 

 maybe caused by accidental pressure. If we compare figs. 

 22 and 23, we find that in the former the somosphere is very 

 small, a faint tint, so to say, surrounding the granular cen- 

 trosomes. In fig. 23, again, the somosphere is much larger 



