1022 The American Naturalist. [November, 
development was first discovered, so far as I know, by E. A. 
Schäfer, who has given a detailed account of the process in the 
ninth edition of Quain’s Anatomy, and has shown there a full 
appreciation of the significance of his discovery. Unfortunately 
Schäfer’s important investigations have received little attention. 
Kuborn has recently confirmed Schäfer’s results in an article 
(Anatom. Anzeiger, 1890) on the formation of blood corpuscles 
in the liver. One can readily study the process in the mesentery 
and omentum of human and other embryos. The essential point 
of Schafer’s discovery is that the non-nucleate corpuscles have an 
?ntra-cellular origin, and arise by differentiation of the protoplasm 
of vasoformative cells. Several corpuscles arise in each cell with- 
out participation of the nucleus; they are, therefore, specialized 
masses of protoplasm, and may perhaps best be compared to the 
plastids of botanists. I venture to propose the name of blood- 
plastids for these structures, since the term corpuscle (globule, 
Korperchen) has no definite morphological meaning. 
Sonsino (Arch. tal. Biol. XI.) affirms that the red blood-cells 
transform themselves into plastids. I have, however, never been 
able to find the intermediate forms in my own numerous prepara- 
tions. I deem it probable that he has seen merely the degener- 
ating stages of the red cells. 
The present article is an abstract of a communication made in 
August last to the American Association for the Advancement of 
Science. Since then Howells’ memoir on the blood corpuscles 
has appeared (Journal of Morphology, YV., 57). The author de- 
scribes the ejection of the nucleus from the red cells, and believes 
that this results in the formation of red plastids. The process is, I 
think, really degenerative, and the resemblance between the non- 
nucleated body of the cell and a true plastid is not one of iden- 
tity. Certainly, until proof is offered that the observations of 
Schäfer, Kuborn, and myself upon the intra-cellular origin of the 
plastids are proved erroreous, the emigration of the nucleus of 
the red-cells cannot be held to result in producing plastids, but 
only to be degenerative. That the red cells degenerate and dis- 
appear has been known; Howells’ valuable observations indicate 
the method of their destruction, 
