Zool.— Vol. I.] EISEN—PLASMOCYTES. 53 



losphere with Heidenhain's middle zone is, however, not 

 apparent, and is rather improbable. This middle zone stains 

 strongly and is plainly granulated, while my hyalosphere 

 stains poorly and is characteristically homogenous, appear- 

 ing like an even, pellucid ring. When we turn to the grano- 

 sphere we can hardly identify it with Heidenhain's inner 

 zone of ectoplasm, this zone staining faintly,' while my 

 granosphere stains deeply. If, again, we consider the po- 

 sition of the inner zone, we find that it surrounds the nucleus, 

 being in actual contact with it, unlike my granosphere but 

 similar to part of my hyalosphere. On account of its stain- 

 ing quality and general appearance I think that my grano- 

 sphere may be more properly identified with Heidenhain's 

 middle zone. If this is so it is probable that my hyalosphere 

 was originally confined to the vicinity of the nucleus but 

 later pushed itself between the plasmosphere and the grano- 

 sphere. Heidenhain's endoplasm cannot be taken into con- 

 sideration as it is only an invagination of the ectoplasm. 

 The innermost spheres in the plasmocyte I can compare 

 only to Heidenhain's microcentrum, though it must be con- 

 ceded that the analogy is not absolutely certain. Heiden- 

 hain understands by his microcentrum, not only the cen- 

 trosomes but also the particular substance which surrounds 

 and converts them, the whole forming a distinct body by 

 itself. This connecting substance — "primary centro- 

 desmose " — must be referred either to my somosphere or 

 centrosphere; or, what is more probable, sometimes to the 

 one and sometimes to the other. In this paper when refer- 

 ence is made to the microcentrum it must be distinctly 

 understood that I leave this point undecided. By micro- 

 centrum I mean the centrosomes together with the nearest 

 visible sphere surrounding them and connecting them with 

 each other. In Heidenhain's figures the divisions of the 

 microcentrum are less distinct from each other than they 

 are in the plasmocytes. The distinction between the grano- 

 sphere and the centrosphere is always very good, especially 

 in successful stains with eosin, as shown in figs. 49, 59, 

 or even 48; and even with toluidine the differentiation is 



Proc. Cal. Acad. Sci., 3DSER., Zool., Vol. I. (4) Oct. 22, 1896. 



