102 CHARLES PACKARD 



through the nucleus suspended in a deUcate non-staining network. 

 After a time (varying in different eggs from forty to eighty 

 minutes) the vesicle breaks down, and the subsequent history of 

 the chromatin is the same as in the case of eggs in which it disap- 

 peared at once. Its dissolution is apparently independent of the 

 presence of the alveolar layer. Here, then, is a case in which the 

 chromatin is not visibly affected by the radium radiations but the 

 protoplasmic activities are much modified, although the structure 

 of the protoplasm itself remains unchanged in appearance. This 

 fact is in opposition to Hertwig's view that only the chromatin 

 elements are affected by the rays. 



The mode of entrance of the spermatozoon into eggs which re- 

 tain their alveolar layer is considerably modified from the normal. 

 The fertilization cone rises up under the point of attachment of 

 the perforatorium as usual, and later sinks into the egg, pulling 

 the sperm head with it. But it takes no stain at all. Figure 12 

 shows an egg killed forty-five minutes after fertilization. The 

 spermatozoon has become implanted in the egg membrane, and 

 has begun to penetrate a short distance into the alveolar layer. 

 No cone is seen. A later stage is shown in figure 10 in which the 

 alveolar layer is still intact and is wider than normal. The sperm 

 heads have penetrated nearly their entii"e length. They never 

 completely enter the protoplasmic area of the egg, but remain in 

 the alveolar layer until it is extruded, at which time some of them 

 continue their course inward. Intermediate stages in this 

 process have not been found. It may be inferred that the 

 sperms enter entirely since at the time that the cortical layer is 

 extruded (in about eighty minutes) none can be found exterior to 

 the egg, while within many may be found in various stages of 

 development. 



The process of maturation in those eggs which fail to extrude 

 the alveolar layer at once is much modified. The germinal vesi- 

 cle disappears normally in the great majority of cases. The 

 chromatin, now free in the protoplasm, may move toward the 

 animal pole where the spindle normally should form, or it may 

 remain in the interior of the egg. Figure 11 shows a case in point. 

 The chromosomes are ill-formed, show no particular arrangement 



