The germ-cells. 675 



The first of them (Fig. 48) is from embryo No. 419. Perhaps 

 it does not really belong to this group. But the resemblance is seen 

 in the pushing of the yolk entirely to one side, and the complete 

 separation of the two cells, formed during a mitosis, from this. They 

 have cut themselves off from the yolk, but have failed to separate. 

 This cutting-otf of a cell, or of more than one, from the yolk-supply 

 has been witnessed and described by Rückert ('87) in his "mega- 

 spheres". And this is an additional reason for the identification of 

 them with germ-cells, or the forerunners of such. 



Two consecutive sections from the next example are shown in 

 Figs. 46 and 47. It is a curious case of degeneration, associated like 

 the preceding with mitosis, and perhaps resulting from it. The two 

 cells — or are there three? — again exhibit the inclination to free 

 themselves from the yolk-mass. The cells are vacuolated, their nuclear 

 contents are in chromatolysis, and duplication is exhibited. 



In all these instances the reasonable interpretation to be put upon 

 this duplication, or twin-condition of the nuclei, is most emphatically 

 that it is a separation of parental constituents. They are more or 

 less loosely joined in life; in death they are separated. 



The final example (Fig. 43) depicts two consecutive sections through 

 a "cell-nest". It is the only instance of this kind of degeneration 

 yet observed (1900), in which yolk was entirely absent. But from the pre- 

 ceding instance, from others undrawn, and — last not least — from 

 Rückert's valuable testimony concerning the "megaspheres" , the 

 reader may be prepared for the statement, that as a preliminary to 

 the degeneration of many of these germ-cells there is often a decided 

 attempt to get free from the yolk- mass. Figs. 47 and 48 illustrate 

 this, and perhaps one is entitled to surmise, that in the example of 

 Fig. 43 this process had already been effected. The resulting cells 

 had then divided by pluripolar mitosis. 



The writer is fairly well acquainted with the literature dealing 

 with pluripolar mitosis, embryological and pathological. But it cannot 

 be recalled, that one peculiarity of this form of cell-division has ever 

 been commented upon. 



Krompecher ('95) has shown, that pluripolar mitosis follows the 

 angles of one or other of the figures of solid geometry; thus, the 

 tetrahedron, octahedron etc. Within limits this is no doubt true. But 

 it does not sufficiently take into account the possible presence of 

 poles of spindles within the figure. Without attempting the to me 

 impossible task of analysing any instances finally resulting from such 



