136 JEREMIAH S. FERGUSON 



long been assumed. That this stage in its most typical form 

 presents those cell pictures which we are accustomed to regard 

 as stellate cells is well known. It is generally recognized that 

 this syncytial stage passes into one in which the fibers appear and 

 the syncytium is replaced by a tissue of cells and fibers. The 

 syncytial stage has been presumed to be preceded by a cellular 

 stage and to those who have traced the origin of the mesoderm 

 from the time of egg fertilization it would appear logical, even 

 necessary, that at a sufficiently early period a cellular character 

 must obtain, though Mall has questioned the preexistence of this 

 cellular condition. The transformation from the cellular to the 

 syncytial condition has been ascribed on the basis of stained sec- 

 tions, to either of two processes: either the syncytium arises by 

 incomplete division of preexisting cells or the syncytium results 

 from the fusion of the preexisting cells. That some syncytia arise 

 by incomplete cell division is very probably true. This appears 

 specially obvious in such placental tissues as the superficial cells 

 of the chorionic villi. I know of no convincing evidence that it 

 does occur in the connective tissues. 



Since I have been unable to observe mitotic figures in the living 

 connective tissue cells of the fish which are under discussion I 

 cannot offer any evidence pro or con the origin of a connective 

 tissue syncytium by incomplete cell division. I have, however, 

 frequently observed a phenomenon which simulates the fusion of 

 processes of adjacent stellate cells after the manner of a typical 

 connective tissue syncytium. In figs. 2 and 8 II the neighboring 

 cells, which were at first entirely distinct and separate, were within 

 a brief period seen to send out processes which on contact appar- 

 ently fused. But of course one cannot say without subsequent 

 fixation and staining of the identical cells, a process presenting the 

 greatest difficulties, that the fusion was actual and complete. 

 Even in stained sections the question is often difficult to deter- 

 mine. While the fusion was apparent I am not at all sure that it 

 was actual. Not, however, in every case when cell came into con- 

 tact with cell did such apparent fusion occur. This is shown in 

 fig. 8 I, in which processes from the cells a and b came into contact 

 tip to tip, yet though fusion seemed imminent it did not occur 



