No. 2.] THE OVARIAN EGG OF LIMULUS. 179 



If we reject the explanation of Leydig, and also that of 

 Auerbach, how shall we account for the first feature of this 

 zone, i.e., the hyaline stage ? Certain features that I have 

 noticed in connection with the germinal vesicle and nucleolus 

 appear to throw light on this question. It was seen that the 

 nucleolus extrudes bodies in the form of vesicles, consisting 

 of a membrane within which is a fluid containing granules 

 (PI. XVI, Figs. I lo-i 13). These vesicles, which I have called 

 " Nebennucleoli," were seen to vary in number, and apparently 

 to appear and to disappear. There is reason for believing that 

 these vesicles lying in the meshes of the nuclear reticulum 

 finally dissolve, and add their contents to the nuclear sap, or 

 karyo-lymph. Where they happen to lie near the periphery of 

 the nucleus, the discharge of their contents extends the area 

 of the germinal vesicle in that direction, thus causing pouches 

 of the nuclear wall (PI. XVI, Fig. 105; PL XIII, Figs. 3, 6-8). 

 The nucleus, to all appearances, is not bounded by a solid wall, 

 but by a special arrangement of the cytoreticulum. 



It has been seen that the germinal vesicle, having become 

 greatly extended, more or less regular in outline, may in another 

 phase of activity become amoeboid, greatly contracted, and 

 apparently devoid of karyo-lymph (PI. XIII, Fig. 5). In all 

 such cases a hyaline area is found to exist outside the germinal 

 vesicle, apparently caused by the entrance into the cytoplasm 

 of the karyo-lymph, which now becomes either a hyaline zone 

 around the germinal vesicle, or in later stages appears as 

 the polar area referred to in another place (PL XIV, Fig. 24; 

 PL XVI, Fig. 104). 



It would appear that this hyaline zone may become lost in 

 the cytoplasm, in which it becomes diffused throughout the 

 interfilar spaces. We may now consider the question of the 

 origin of the internal granular zone of the egg. 



The definite yolk spheres appear only after the egg is dis- 

 charged from the follicle into the ovarian tube. It is hardly 

 necessary, therefore, to consider the explanation of an internal 

 zone in the egg of the fish offered by His, as his well-known 

 theory of migrating granular cells would not apply in this case, 

 and, so far as I know, has never been seriously considered in 



