Zool.— Vol. I.] EISEN—PLASMOCYTES, 29 



somosphere has carried with it an envelope of centro- 

 sphere; while in figs. 28 and 36 each centrosphere is fully 

 separated from the other. In fig. 28 a further stage has 

 been reached, as here each centrosphere is surrounded by 

 an envelope of granosphere. At a yet more advanced stage 

 this granosphere is surrounded by an envelope of hyalosphere 

 and plasmosphere, as seen in figs. 37, 38, and 39. The next 

 stage consists in an entire separation of the new spherical 

 body from the plasmocytoblast. In other words the plasmo- 

 cytoblast has divided into two or more distinct bodies which 

 have gradually freed themselves from all connection with 

 the nucleus, or rather from the thin layers of cytoplasm 

 yet adhering to the nucleus; the nucleus has continued to 

 disintegrate, while new plasmocytes have steadily developed 

 until they have become free and independent elements of 

 the blood. That these new bodies, or blood elements, are 

 something entirely distinct from mere fragments of the cyto- 

 plasm is evident from several observable facts. The plas- 

 mocytes increase in size, which again shows an independent 

 growth undoubtedly caused by the taking up of nourishment; 

 they have also moved away from the vicinity of the nucleus, 

 showing independent movement; and finally, they have 

 changed their form from a mere fragment to a finished, 

 symmetrical body. The various spheres or envelopes of 

 the new plasmocyte do not show any great irregularity, but 

 instead exhibit a surprising regularity, especially as regards 

 the two exterior spheres, the closing up of which forms 

 the last step in the formation of the plasmocyte. Figs. 

 28«, 32$, 37, 38s, 385, 39, etc., represent plasmocytoblasts 

 in the last stages of development, the plasmocytes being 

 almost perfected and ready to separate. In 37 the plasmo- 

 cyte is entirely formed, while in 38s and 39 it is yet con- 

 nected with the old fusiform element by a narrow shaft 

 of plasmosphere. 



XI. The Plasmocytes. 



General Remarks. — In the foregoing I have endeavored 

 to show how the archosomes, or microcentra, of the plas- 



