234 K. MITSUEÜRI. 



of segrnentation.* As the figure shows, the primitive plate be- 

 co'nes continuous with both the epiblast and the lower layer at its own 

 periphery. I am thus unable to find any independent sheet of cells 

 which lies below the primitive plate, and with which alone the 

 lower layer of the surrounding- parts becomes continuous, as Wencke- 

 hich (No. 15, Fig. 1) and Mehnert (No. 8, Figs. '20 and 21) and Will 

 (No. 21, Fig. 49) have found. On this point Virchow's observations 

 (No. 14) seem to be similar to mine ; Will also sees no such inde] »en- 

 dent sheet of cells in earlier stages (N(\ 19 Fig. 1, No. 21). I am 

 also unable to find such a sharp line of demarcation between the 

 shield and the primitive plate as is given in Will's Fig. 1 (No. 

 19f) : the primitive plate passes gradually into the epiblast both 

 anteriorly and posteriorly. 



The yolk globules in this series of sections are generally spheroidal 

 with a uniform yellow tint. Generally speaking, they are markedly 

 fine immediately below the blastoderm, and become larger farther 

 below (See Fig. 9) : of their especially small size iinderneatVi the 

 primitive knob, I have already spoken. I agree with Virchow 

 (No. 14, )). 67) in thinking that the dark granules which Mehnert 

 describes in the yolk-globules (Xo. 8, Figs. 20 and 21) are artificial 

 productions made in the course of preparing sections. 



I regret that I was unable to obtain the oTowino- edo-e of the 

 blastoderm which \\ould no doubt present interesting phases of growth 

 as observed by Virchow (No. 14) and Duval (No. 2). I am therefore 

 luiable to thro\N' much light on many questions bearing on cells found 

 in the yolk. I may however mention that in the series from which 

 Fig. 9 is taken, two kinds of cells are found imbedded in the 

 volk. Theii' nature is not donr to me. Tlic inorc iiumon~»us kind T 



* Will appears to be of the same opinion (No. 21). 



t This sharp deiuarention is insisted on still more strongly in Will's recent paper {Xo. 21). 



