lioyal Microscopical Society. 59 



though already fully detached, they had as yet not entirely left the 

 concave depression (Fig. 6, c). 1 further observed a number of 

 others which distinguished themselves from the mature corpuscles 

 by their biconvex surfaces ; these had very probably been detached 

 from their mother-body not long before, and, in consequence, not yet 

 attained the final biconcave form (Fig. 6, c). Finally, I observed 

 still a number of very pale flat bodies, resembhng a flat disk. The 

 most of these were seen to have collected in groups (Fig. 6, e) ; 

 they also represented young blood corpuscles, but seem to have been 

 derived from another source, hereafter to be mentioned. 



In examining the blood of the fresh pulp of the spleen of the 

 same embryo, I found, in addition to these elements just described, 

 also a considerable number of free nuclei and cells, generally 

 collected in small masses. The former were bounded by a fine 

 double contour. Their interior was filled with granules. The 

 latter consisted of the same nuclei, enveloped in a granular mass, 

 and differed in no way from the colourless blood corpuscles of the 

 adult (Fig. 6,/). 



One month later, in the beginning of the fifth month, the 

 primary endogenous formation of young colom-ed blood corpuscles 

 goes on still more slowly. Nevertheless, a certain number of 

 mother-corpuscles, containing but one embryo-corpuscle, are still 

 observed (Figs. 7 and 8, a). This is especially the case in the 

 blood of the fresh pulp of the spleen. A small number of others 

 I also observed here, which had already rid themselves of their 

 brood, the traces of which they still bore in the form of one or two 

 concave depressions (Fig. 8, h). The soft margins of the latter were 

 kept in a flapping-like motion, when the blood corpuscle, carried 

 by the current, glided along under the covering glass while turning 

 upon itself. Some of these bodies still contained an embryo- 

 corpuscle, a fact which shows that the mother-corpuscles of this 

 period are still capable of generating two embryos, though each 

 successively. Besides a large multitude of mature coloured blood 

 corpuscles (Fig. 7, c), a considerable number of young biconvex ones 

 {d) were also observed, which seemed, as before mentioned, to have 

 been detached from the mother-bodies but a short time before. The 

 colourless elements of the pulp of the spleen showed the same cha- 

 racter as those of the adult spleen; they consisted of granular 

 nuclei, nucleated cells, and fully-developed colourless blood cor- 

 puscles (Fig. 8, c). In the heart I met with the same elements, 

 with the exception of the granular nuclei and cells. The colourless 

 blood corpuscles here met with seemed to be in different stages of 

 development, for a considerable difference existed in their diameters, 

 some of them were even smaller than a coloured corpuscle. The 

 greater part of them contained but one nucleus, others two. The 

 most of these bodies were round, while the rest were irregular 



VOL. XI. F 



