MORPHOLOGY OF THE BLOOD CORPUSCLES. 431 



term corpuscle (globule, Korpercbeu) lias no detiiiite morphological 

 meaning. 



Sonsino {Arch. Ital. Biol, xi) affirms that tbe red blood cells trans- 

 form themselves into plastids. I have, however, never been able to 

 find tlie intermediate forms in my own numerous preparations. 1 deem 

 it ])robable that he has seen merely the degenerating 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's memoir on the blood corpuscles has appeared 

 {Journal of Morphology, iv, 57). The author describes the ejection of 

 the nucleus from the red cells, and believes that this results in the for- 

 mation of red plastids. The process is, 1 think, really degenerative, 

 and the resemblance between the non-nucleated body of the cell and a 

 true plastid, is not one of identity. Certainly, until proof is offered that 

 the observations of Schiifer, Kuborn, and myself, upon the intra cellu- 

 lar origin of the plastids are proved erroneous, the emigration of the 

 nucleus of the red cells can not be held to result in producing plastids, 

 but only to be degenerative. That the red cells degenerate and disap- 

 pear has been known ; Howells's valuable observations indicate the 

 method of their destruction. 



The above review shows that the vertebrate blood corpuscles are of 

 three kinds: (1) red cells; (2) white cells; (3) plastids. The red and 

 white cells occur in all (f) vertebrates; the plastids are confined to the 

 mammals. The red cells present three chief modifications; whether 

 the primitive form occurs in any living adult vertebrate I do not know ; 

 the second form is ])ersistent in the Ichthyopsida, the third form in the 

 Sauropsida. According to this we must distinguish : 



A. — One-celled blood, i. e., first stage in all vertebrates; the blood 



contains only red cells, with little protoplasm. 

 B. — Two-celled blood, having red and white cells ; the red cells 

 have either a large, coarsely granular nucleus (Ichthyopsida), 

 or a smaller, darkly staining nucleus (Sauropsida, mamma- 

 lian embryos). 

 0. — Plastid blood, without red cells, but with white cells and red 

 plastids; occurs oidy in adult mammals. 

 Mammalian blood in its development passes through these stages, as 

 well as through the two phases of stage B, all in their mitural sequence ; 

 the ontogenetic order follows the i)hylogenetic. 



I pass by the numerous authors Vhose views confiict with mine, 

 partly because the present is not a suitable occasion for a detailed dis- 

 cussion, partly because those authors who have asserted the origin of 

 one kind of blood corpuscle by metamorphosis from another have failed 

 to find just the intermediate forms ; it seems to me thereiore that most, 

 at least, of the opposing views collapse of themselves- 



