No. 2.] THE EGG OF BUFO LENTIGINOSUS. 307 



Fig. 9. Here the interior of the structure contains several 

 large and many smaller vacuoles ; the latter have arisen pre- 

 sumably from the breaking down of the larger ones. In an 

 older stage (Fig. 10) the vacuoles are very numerous and they 

 are more nearly uniform in size. These nuclear bodies de- 

 crease considerably in volume during the formation of the first 

 polar spindle and stain less intensely, always, however, retain- 

 ing their vacuolated appearance. They are frequently found 

 near the upper pole of the Q^g during the extrusion of the 

 polar bodies, but they are soon after absorbed and no trace of 

 them can be found in the later fertilization stages. As these 

 bodies first appear during the hibernation period, it is impossi- 

 ble to say whether they arise from the fusion of two or more 

 small nucleoli, from the rapid growth of a single nucleolus, or 

 whether they are only a late secretion product of the germinal 

 vesicle. The last assumption seems the most probable, as these 

 structures apparently undergo an entirely different process of 

 absorption from that of the other nuclear bodies. 



Another egg from the same series as the one just described 

 shows the next steps in the process of maturation. The sub- 

 stance around the germinal vesicle has differentiated into two 

 parts (PI. XXVIII, Fig. 7) : the one nearer the vesicle is a 

 dense band of uniform thickness (Fig. 7, LR), composed of 

 very fine, closely packed fibers, the greater number of which 

 run parallel to the nuclear membrane ; the other part consists 

 of coarse homogeneous granules imbedded in a fine reticulum 

 which is continuous with the denser portion above and also 

 with the cytoplasm around it (Fig. 7, A). 



The lower pole of the germinal vesicle is apparently the 

 place where the disintegration processes originate. In this 

 region the nuclear membrane first becomes very irregular and 

 then gradually disappears ; here, too, the finely granular nuclear 

 sap first begins to be formed into large granules, as described 

 by Born in the germinal vesicle of the Q.gg of Triton. 



As dissolution continues, the germinal vesicle becomes filled 

 with round, deeply staining granules of nucleoplasm. In the 

 center and upper portion of the vesicle the granules, which are 

 very small, form a loose reticulum in which the chromatin 



