30 Mary Blount. 



kein Fall bekannt, dass die Wanderkorper ins Innere normaler 

 vegetationsfahiger Zellen eingedrungen waren und dieselben zerstort 

 batten." 



Are these cells supernumerary spermatozoa ? Their inconstant ap- 

 pearance argues for this origin. Possibly they are sperms that have 

 entered late. The influence of the egg which otherwise would have 

 drawn them into the granular cytoplasm may have ceased just after 

 they had gone through the vitelline membrane, and they may have 

 migrated peripherally in the perivitelline fluid to the region of the 

 periblast. Or they may have entered late in the region where they 

 are now found. They are usually in the region of the periblast. 

 Their entrance directly into the periblast without migration from 

 the blastodisc would make them comparable with the spermatozoa 

 which enter the vegetative pole of the amphibian egg, or those which 

 Ballowitz ('03) has described as entering directly into the yolk 

 of the adder. Their usual degeneration at about the time when 

 the supernumerary sperm nuclei degenerate in the periblast also 

 argues for their sperm origin. 



Moreover, we can hardly believe that so many follicular cells 

 would enter at one place as to give such a large mass as is found in 

 Fig. 12a. Even by repeated division until the time when this egg 

 was killed, six hours after fertilization, two or three follicular cells 

 which might enter together could not form so many as are in this 

 mass. 



Evidence of the Disappearance of the Supernumerary Nuclei in 

 the Pigeon and Comparison with Other Meroblastic Vertebrate 

 Eggs. — As I follow the figures and descriptions of the reptilian 

 and selachian eggs, I must believe that in those forms, as in the 

 pigeon, the supernumerary nuclei degenerate early, and that the 

 "yolk nuclei" of later cleavage are periblast nuclei derived from 

 the cleavage nucleus. Kiickert's ('99) Figs. 2, 3, 4 and 8, Tab. 

 LII, give surface views of successive stages of Torpedo eggs. With 

 the progress of development, the accessory cleavage disappears. In 

 the pigeon's egg, with the disappearance of the accessory cleavage at 

 the surface, there is also the absence of supernumerary nuclei in the 

 sections. But it may be suggested that the egg in which I saw no 



