94 CHARLES PACKARD 



vial of such a size that it exactly fitted into the depression in the 

 capsule in which the radium salt was held. The radium in this 

 experiment was equal to 4 mg. of the pure bromide. The drop of 

 spermatozoa was so spread out on the bottom of the vial that it 

 formed a thin layer, all parts of which must have received equal 

 radiation. A control experiment was made by putting another 

 small drop into a similar vial which was placed near the other, 

 but screened from it by two sheets of lead. As a rule, the sper- 

 matozoa were radiated for at least twelve hours, for it was found 

 that shorter exposures produced very slight effects. After so long 

 a treatment the motility of the spermatozoa seemed to be un- 

 changed. Indeed they showed no signs whatever by which to 

 distinguish them from the control or from perfectly fresh sper- 

 matozoa. These results are in accord with the statements of G. 

 Hertwig ('12) in regard to the spermatozoa of sea urchins. 



The phenomena of fertilization that can be observed in the 

 living egg are normal. Great numbers of spermatozoa collect 

 at the periphery of the eggs and can be seen to be pushed away by 

 the gradual outflow of jelly which forms as soon as the successful 

 spermatozoon is implanted in the egg membrane. If india ink 

 is added to the water it becomes evident that no jelly is extruded 

 at the point of attachment, the spermatozoon appearing to lie at 

 the apex of a cone of ink which marks the region where the jelly 

 is lacking. The time elapsing between the addition of the sperm 

 and the outflow of jelly appears to be normal. Soon after the 

 implantation of the spermatozoon the fertilization cone develops, 

 reaching up to the surface of the egg membrane just below the 

 point of attachment. The further progress of the fertilization 

 phenomena can be seen best in sections. 



Eggs killed thirty minutes after insemination show the sper- 

 matozoon, entirely normal in appearance, still external to the 

 egg, with the perforatorium extending through the egg and. into 

 the substance of the fertilization cone. A little later the cone 

 is retracted, pulling with it the sperm head and egg membrane 

 so that the latter forms a small depression in which the former 

 lies. Then the sperm head begins to be drawn out, penetrating 

 further into the cone, and developing about its perforatorium 



