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THE AMERICAN NATURALIST [Vol. LI 



matter into tvhich part of the organism they are trans- 

 planted/' This assumption may apply to a number of 

 developmental processes in the organism, but the state- 

 ment is only part of the truth. Years of study of the loose 

 mesenchyme and of the differential processes, observed 

 in this tissue, have yielded a few results, which most de- 

 cidedly do not harmonize with the generalization above 

 quoted. 



The loose mesenchyme, which appears in the early 

 stages, is characterized by its ubiquity and by lack of 

 obvious special function, if its mere presence between 

 other organs has not to be considered as function. The 

 mesenchjTne is a sjTicytimn of similar cells, the structure 

 and most probably the metabolism of which is little if at 

 all changed, while the cells remain as constituent parts of 

 the syncytium. Influences of local origin which might 

 change the metabolism of some of the cells are inhibited 

 by continuous unimpeded flow and intermixture of sub- 

 stances in the undivided bodies of the cells. 



Cells of tlie loose mesenchyme become isolated from the 

 syiicytium in many ])arts of the organism. This process 

 ot" ixtlation i< ditVuM'. \]\ some parts of the organism it 

 atlV.-t^ nicivly a ^niall iiuiulx-r of cells, in others it is 

 di>play('(l witli u;vi",\\ intensity. Scattered free cells or 

 lai'ge gr()U])s of them are formed. The cause of such 

 isolation f If it is not possible to formulate it in positive 

 terms, at least it can be stated, that it does not depend 

 nptni prcdcstlnaiion, centered in the syncytium itself, 

 since isolation of cells fi'oni a mesenchymal syncytium 

 can Im- ui'catly iiiten.-ified expeiimentally. Large groups 

 of free cells develo]* in the eiiihi'vo after certain grafts 

 on its allantois in regions in which normally the cells 

 would retain their syncytial connections. 



The free ameboid cells isolated from the mesenchymal 

 syncytium diff(M- from the cells of their maternal basis in 

 inan\- respects. Th(>ir metal)o]lsiii is no longer conti'olled 

 am! i-'mil.itMl !li.' inrMhulKin of the whole colony of 

 me-encii\ itial li>>ue. Ixilaled tlie\ are very active, grow 



