Zool— Vol. I.] EISEN—PLASMOCYTES. 1 3 



instances I have seen the inner spheres around the centro- 

 somes stand out sharply, while the nucleus and other parts 

 of the cytoplasm were in the last stages of disintegration; 

 but I have never seen such a separation of the centrosomes 

 and centrosomal spheres as takes place in the fusiform ele- 

 ments, and, judging from my observations, the microcentrum 

 of the leucocyte does not survive. It is undoubtedly less 

 differentiated and organized than that of the erythrocyte. 



Plasmocytes. — I apply this name to a hitherto undescribed 

 element in the blood, first observed by me in the blood 

 of Batrachoseps, and later also in some other batrachians and 

 reptiles, as well as in that of man. These new elements are 

 much smaller than the average erythrocytes, if, indeed, 

 an average can be struck for a corpuscle with such extreme 

 and irregular variations as the erythrocytes in the blood of 

 Batrachoseps. The plasmocytes are only slightly larger 

 than the smallest erythrocytes of the Batrachoseps blood, 

 and similarly, only a little larger than the red blood cells of 

 the human blood ; but even the plasmocytes vary consider- 

 ably, and some are found which are smaller than the human 

 red blood cells. They are generally chiefly characterized 

 by the absence of a cell membrane, and out of about a thous- 

 and plasmocytes only six showed a rounded outline and what 

 I considered a cell membrane. The general form is that of 

 a round or oblong star-shaped body, with more or less frayed 

 or amoeboid projections of the outer layer, while the inte- 

 rior is arranged in varying concentric zones. They occur 

 in large numbers, are more numerous than the fusiform ele- 

 ments, and much more numerous than the nucleated red 

 cells. The object of this paper is to establish the identity 

 of these plasmocytes; to trace their origin; to follow their 

 development; and to demonstrate and prove that they are 

 composed of the centrosomes and archoplasm (with part of 

 the cytoplasm) of the nucleated erythrocytes, having dis- 

 engaged themselves from the degenerating and dissolving 

 parts of the fusiform corpuscles, surviving in the blood 

 serum as free and independent elements capable of growth 

 through assimilation of food, and taking their place as blood 



