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by the side of the chromatin. Haematopoiesis occurs in various 

 ways in the Tarsius-placenta. Every now and then we notice a 

 nucleolar body (the nuclear membrane surrounding it becoming 

 partially indistinct and then disappearing) being set free and mixing 

 up with circulating blood-corpuscles from which it cannot possibly 

 be distinguished. Besides this simpler mode of origin we find 

 another in which large-sized, so-called giantcells with lobulated 

 and gemmating nuclei play a part. Numerous nuclear fragments 

 are set free from it, the nucleus itself vanishing in the process. 

 The fragments are of equal size, behave in a corresponding way 

 towards the most different staining reagents and might bo designated 

 as „haematogonia". All the intermediate stages between these hae- 

 matagonia and normal blood-corpuscles were observed and similarly 

 their development out of the enlarged nucleus and not out of the 

 cellplasm could be demonstrated .^tIt are not only maternal but also 

 embryonic trophoblastoells which partake in this haematopoiesis 

 under similar phenomena of proliferation ; the blood-corpuscles thus 

 formed are also caught up by the maternal blood and circulate 

 with it. 



A destructive significance cannot reasonably be given to the giant- 

 cells in the Tarsius-placenta : they are decidedly constructive ele- 

 ments, which furnish not only blood-corpuscles, but also the walls 

 of bloodlacunae. This double part is often played by solid strands 

 of cells in lovser vertebrates. 



It deserves attention that the participation of giantcells with 

 characteristic proliferating nuclei in the formation of blood in the 

 bone-marrow, the liver and the spleen of mammals was expressly 

 recognized by Neumann, Kölliker, Peremeschko, Küborn, Saxer, 

 Eliasberg, Freiberg a. o. Many of them look upon the prolife- 

 ration of the nuclei of these giantcells (which are perfectly distinct 

 from those other giantcells, the osteoclasts which occur in their 

 immediate vicinity in the bone-marrow) as the first step in the 

 formation of blood-corpuscles, although none of them has expressed 

 the opinion that these latter should not be looked upon as cells but 

 as nuclear derivates. As soon as we do this, on account of what 

 we have observed in Tarsius, light is also thrown on the develop- 

 ment of the fullgrown non-nucleated corpuscles out of embrvonic 

 nucleated ones, a phenomenon which as above indicated is undoub- 

 tedly comparable to it. 



Simihir haematopoietic processes are noticed in the placenta of 

 Tupaja, which differ in detail but agree in general outlines with 

 what has here been described for Tarsius. 



12* 



