1 78 MUNSON. [Vol. XV. 



narrow bridge or stalk. Auerbach, on the other hand, regards 

 it as the expression of a condensation of the cytoplasm, which 

 takes place previous to the division of the cell, and which ulti- 

 mately results in the formation of a spherical body, the sphere, 

 or " Nebenkern." 



Such an explanation of the zone around the germinal vesicle 

 in the egg of Limulus cannot be offered, inasmuch as it appears 

 during the period of growth of the egg, when it has ceased to 

 divide, and often after it has attained to a considerable size. 

 This appears to be true in the fish egg also, according to the 

 observations of Scharff. He considers the outer zone as cor- 

 responding to the " Rindenschicht " of Eimer, which the latter 

 believes to be identical with the " Zonoid schicht " of His. 



One objection to applying Auerbach's interpretation to the 

 inner zone of the egg is the sharp line which in certain stages 

 separates the two zones (PL XKI, Fig. 16). This feature is 

 peculiarly striking in the living egg of Limulus, and is espe- 

 cially emphasized by Pfliiger as observed in the egg of the cat, 

 and appears to have attracted the attention of Schulin in the 

 egg of the bat and in the human ovum, and also of Will in 

 the egg of Colynibctcs fusctts. It is, of course, difficult to say 

 what effect a condensation might have. 



The changes of the inner zone from a hyaline to a granular 

 condition, observed by Pfliiger in the egg of the cat, and which 

 is so evident in the egg of Limulus (PI. XIV, Figs. 19, 24), 

 appear to be evidence of chemical changes taking place in the 

 interfilar amorphous substances immediately surrounding the 

 germinal vesicle. This may, of course, be accompanied with 

 an increased condensation of the reticulum; but it would seem 

 that the latter would be more apparent than real, and due rather 

 to the increase in the amorphous granules. The sharp limita- 

 tion of the inner zone in certain phases of the contained gran- 

 ules, it seems to me, points to differences in composition of the 

 amorphous or granular matrix in which the cytoreticulum lies 

 (PL XIV, Fig. 48). 



In endeavoring to account for the existence of this inner 

 zone, there are four important elements which demand atten- 

 tion. 



