( 876 ) 



the interglandular tissue and in the cells, lining the just mentioned 

 spaces, phenomena take place which force us to the conclusion that 

 a great number of these blood-corpuscles originate in loco. When we 

 follow these phenomena up to their earliest appearance, we iind 

 that in the dilated glands in many [daces compact cell-heaps are 

 formed, which sometimes lie quite loose in the gland, but in other 

 cases are still found in direct connection with the cell-lining of the 

 gland. We must assume that this latter condition represents the 

 original one and that consequently we have here an epithelial proli- 

 feration by which new cell-material is carried into the region of 

 the future placenta. 



The final product of these lumps of tissue, which in early stages 

 appear so distinctly as cell-heaps, is an agglomerate of non-nucleated 

 blood-corpuscles. The gradual transition of the nucleate cells into the 

 blood-discs may be followed step by step by successively comparing 

 preparations of the youngest and subsequent stages: often in one 

 preparation all transitions are found together. It then appears that 

 the conclusions I drew for Tarsius and Tupaja in 1898 are confirmed 

 here, viz. that the blood-discs are produced by gradual transitions 

 from the modified nuclei of the above-mentioned cell-heaps and that 

 in this process transitional stages are generally found, comparable to 

 what I called "liaematogonia" in the above-quoted paper. They re- 

 semble polynuclear leucocytes from which they may be distinguished, 

 however (also according to Maximow and Siegenbeek van Hkukelom; 

 see report of the meeting of the Amsterdam Academy of Nov. 26, 

 1898), by certain characteristics. This phenomenon has been more 

 fully investigated by Poljakoff, who also regards the non-nucleate 

 corpuscles as nuclear derivatives and not as cells, deprived of their 

 nuclei. In his paper x ) numerous illustrations are given of stages 

 corresponding to my liaematogonia. It appears from the literature, 

 mentioned by Poljakoff that my paper of J 898, preceding his 

 publication, was unknown to him: the concordant results which we 

 have obtained at an earlier date, are confirmed in a striking manner 

 by the phenomena seen in Galeopithecus. 



But blood-corpuscles are also produced by other sources besides 

 these epithelial glandular proliferations. Between the dilated glands 

 we find in Galeopithecus in the trophospongia-tissue very conspicuous 

 groups of large cells with a big, but circular nucleus. They show a 

 tendency to lie together in nests, which nests are more or less kept 

 together by elongated cells, forming a spurious wall which distantly 

 remind us of an endothelium. 



!) Biologie der Zelle. In Arch. f. Anat. u. Phys. Abth. 1901. PI. I and II. 



