498 Mr. C. E. Walker. [May 15, 



The mass of protoplasm which is left without a nucleus may be dismissed 

 in a few words. It closely resembles what has been described elsewhere as 

 the red blood corpuscle after it has lost its nucleus, and before it has become 

 differentiated to its concavo-convex shape.* Whether some red corpuscles 

 arise in this way must remain doubtful at present. There is, however, 

 nothing against this being the case in the observations referred to, as red 

 corpuscles seem to arise in the spleen, as well as in the bone-marrow. 



The case of the leucocyte with a nucleus containing a double complement 

 of chromatin and linin, however, calls for a careful consideration. 



In a previous communication upon the life-history of leucocytes, observa- 

 tions were recorded which seemed to show that some, at any rate, of the 

 leucocytes in the bone-marrow passed through the Meiotic Phase, and, after 

 the number of the chromosomes had thus been reduced to one-half the 

 normal somatic number, many post-meiotic generations occurred both in 

 the bone-marrow and in the lymphatic glands, in which the reduced number 

 of chromosomes was retained.! A comparison was made between these 

 phenomena occurring among leucocytes and what happens in the case of 

 many plants. At the same time, it was suggested that, while the large 

 number of post-meiotic generations, and the fact that but few of the cells 

 of these generations were destined to conjugate with other reduced cells 

 in the case of plants, offered a parallel with what apparently happened 

 in the case of leucocytes, an important difference existed, in that there 

 was no evidence that any among the post-meiotic generations of leucocytes 

 ever reached a stage where they conjugated with other reduced cells. 



The observations recorded in the present communication suggest that 

 this comparison may now be carried much further, not only between certain 

 phenomena exhibited by plants and leucocytes, but also between those 

 exhibited by plants and unicellular organisms on the one hand and 

 leucocytes on the other. This further comparison depends upon the inter- 

 pretation placed upon the absorption of the nucleus of one leucocyte 

 by another, and is only possible if this is regarded as a process of 

 fertilisation. 



There is a considerable amount of evidence that these leucocytes in which 

 the fusion of nuclei takes place have passed through the Meiotic Phase. The 

 members of this particular class of leucocytes are frequently found to be dividing 

 mitotically, very commonly exhibiting the reduced number of chromosomes. 



* C. E. Walker, " On the Origin and Differentiation of the Eed Blood Corpuscles in 

 Mammals," 'Trans. Path. Soc. London,' vol. 58, Part I, 1907. 



t C. E. Walker, " Observations on the Life-history of Leucocytes," ' Eoy. Soc. Proc./ 

 B, vol. 78, 1906. 



