30 CALIFORNIA ACADEMY OF SCIENCES. [ 3 d See., 



mocytoblasts, have gradually receded from the immediate 

 vicinity of the nucleus ; how they have clothed themselves 

 with envelopes of the outer cytoplasmic layers, or spheres; 

 and finally, how they have entirely separated themselves 

 from the fusiform corpuscles, henceforth existing as plasmo- 

 cytes in the blood serum. These new elements possess 

 properties which must characterize them as independent 

 corpuscles. These properties have already been referred 

 to as follows : Assimilation of food through phagocytosis, 

 or through the blood serum; exhibition of independent 

 movements which have enabled them to separate from their 

 connection with the fusiform corpuscle and to live an inde- 

 pendent life in the blood serum; and further, they have, 

 from the beginning, been something else than mere frag- 

 ments, each one being surrounded by ringlike spheres or 

 zones of differentiated protoplasm, one exterior to the other, 

 an organization which is not found in fragments. 



The plasmocyte is thus characterized by the possession of 

 form; interior and symmetrical organization; independent 

 movement, both as a whole and as regards the separate 

 spheres of the microcentrum; and growth by means of 

 phagocytosis, which includes the process of digestion in 

 the granosphere and in the somosphere. 



All these properties also characterize a cell; but the 

 plasmocytes are not cells; they lack, in fact, two most 

 essential characteristics of a perfect cell: they possess no 

 nucleus, and are not generally surrounded by a cell mem- 

 brane. 



Homology of the Plasmocytes and the Plasmocytoblasts. — I 

 have carefully examined about one thousand plasmocytes, 

 more or less, under very many stains, and find that while 

 they vary, they do so only within certain limits, and with 

 the exception of a dozen all told they present the same 

 general structure. Comparing them with the plasmocy- 

 toblasts in various stages of development, we find that 

 the plasmocyte possesses every characteristic found in the 

 advanced plasmocytoblast, while it does not possess a 

 single characteristic which is not also found in some plas- 



