SUMNER: KUPFFER'S VESICLE 79 



XI. SUPPLEMENT. 



Since writing the foregoing pages, I have had an opportunity of putting to ex- 

 perimental test certain of the views therein maintained. At Naples, during the 

 past July, I carried on experiments with a view to determining the manner of for- 

 mation of the embryonic body in Exocoetus sp. My results will shortly be pub- 

 lished. I will, however, briefly record the confirmation of two of the conclusions 

 maintained above. 



First, that the germ-ring passes, in large part at least, into the embryo. Proof : 

 Glass needles were inserted into the eggs, piercing the germ-ring far laterad to the 

 caudal end of the embryo during an early stage. At a late period, the point of in- 

 sertion of the needle was, in certain instances, found to be close beside the caudal 

 end of the embryo. In these cases the latter was conspicuously bent as if the pos- 

 terior part had been drawn towards the needle. One can only conclude that the 

 segment of the germ-ring which lay between the needle and the embryo had passed 

 into the latter, but the germ-ring being held fast on one side, the embryonic body 

 itself was drawn in that direction. 



Second, that, at least after a certain period, there occurs a process of confluence, 

 rather than one of concrescence. Proof: In cases where a needle was inserted at 

 the mid-caudal point of the early embryo, the embryo none the less continued to 

 grow, but necessarily in a forward instead of a backward direction, while the blasto- 

 pore continued to close in a seemingly normal manner. Indeed there was nothing 

 to show that the usual concentric growth of the blastoderm had been disturbed. 

 The only possible inference is that the germ-ring material entered at a point anterior 

 to the needle causing the embryo to elongate in the only direction in which it was 



free to move. 



FRANCIS B. SUMNER. 



C. C. N. Y. Sept. 21, 1900. 



