Zool.— Vol. I.] EISEN—PLASMOCYTES. 43 



exerting itself on the nucleus, caused the cell wall to rupt- 

 ure and the fusiform corpuscle to be set free in the serum. 

 The very fact that the centrosome and plasmospheres sur- 

 vive — nay, grow, develop, and continue an independent 

 life — while the nucleus perishes, points to this conclusion. 

 The nucleus of the fusiform corpuscle is, as compared to 

 the nucleus of the erythrocyte, always in a state of degen- 

 eration. The various kinds of chromosomes are neither 

 distinguishable in shape nor color, and consist of a mere 

 irregular mass of globules of various sizes, more or less con- 

 centrated towards the center. There is an entire absence 

 of those fine and exquisite details found in every perfect 

 nucleus. The nuclear membrane — the caryotheca — is also 

 frequently ruptured, and we can see small parts of the nu- 

 clear plasma diffusing in an irregular way through the cyto- 

 plasm, indicating dissolution and decay. 



Dr. A. Dehler, who was the first to demonstrate the micro- 

 centrum in the erythrocytes of the chicken embryo, de- 

 scribes and figures only one set of centrosomes in the resting 

 blood cell. Also M. Heidenhain, who has so studied in detail 

 the nature of the leucocyte, refers only lightly to the micro- 

 centrum of the erythroblast. In figs. 15 and 16 ("Neue 

 Untersuchungen ") he figures two nucleated red blood cells 

 with centrosomes partly visible in the cytoplasm. Fig. 16 

 interests us most because the nucleus with the polar pro- 

 jections bears a strong resemblance to the fusiform elements 

 of Batrachoseps blood. Heidenhain does not enter upon any 

 detailed description of these cells but simply states that ac- 

 cording to his conclusions the ejection of the nucleus is 

 caused by the tension of the aster rays, in conformity with 

 his now well known tension theory. He believes, also, that 

 after the ejection of the nucleus the centrosomes remain in 

 the erythrocyte. Whatever may be the case with the erythro- 

 cytes of the rabbit, I am positive, as regards the fusiform 

 elements of the Batrachoseps blood, that the centrosomes 

 remain in the plasmocytoblast. 



The Ultimate Fate of the Plasmocyte. — A remarkably 

 small proportion of plasmocytes show signs of dissolution, 



