-> 1 5 JORDAN. [Vol. VIII, 



elements begin to show signs of degenerative change, and in 

 eo-o-s ten hours old — just before the beginning of the first 

 cleavage plane — they are in a condition of well-marked 

 atrophy. This is evinced by the disappearance of the mem- 

 brane and by the mixing of the chromatin through the Qgg 

 substance. I have been able to identify degenerating accessory 

 nuclei in the four-cell stage, but not beyond. 



v. Bambeke ('70) was one of the first to afhrm that several 

 spermatozoa normally entered the amphibian egg, but his state- 

 ments were on the whole regarded as relating to abnormal 

 conditions, and were not given the credence to which I think 

 they were entitled. Since his observations were made upon 

 the eggs of certain Urodela, and since none of his critics have 

 repeated his observations on these particular species, but have 

 reasoned themselves into incredulity solely through their own 

 negative results upon the eggs of other animals, there seems 

 no o-ood reason for refusing our acceptance of v. Bambeke' s 

 observation. Negative observations upon the eggs of one 

 animal hardly furnish an adequate basis for scepticism regard- 

 ing positive phenomena in the eggs of related animals. Kupffer 

 (■82) also has affirmed the normal entrance of several sperma- 

 tozoa into the amphibian egg. 



Physiological polyspermy has been observed, moreover, in the 

 eggs of other vertebrates. Two of the most important cases I 

 may briefly mention. Ruckert ('91, '92% '92^) has described 

 some remarkable phenomena of this character in the eggs of 

 Selachians {PristiimLs, Torpedo). A number of spermatozoa 

 normally enter the egg, develop like the chief male pronucleus, 

 and, at the formation of the first cleavage nucleus, divide caryo- 

 kinctically, and give rise, in part, at least, to the parablast 

 nuclei, or '' Merocytenkernc'' ! These Merocytenkerne which 

 arise thus independently from accessory spermatozoa are 

 distinguished from the nuclei of the " Furchungskern " 

 by a smaller number of chromosomes — " hochstens die 

 Halfte"! " Alle Merocytenkerne der jungen Furchungsta- 

 dien, welche eine reduzierte Zahl von Chromosomen besitzen, 

 sind Abkommlinge von Spcrmakopfen, (Ruckert, '92^ 

 p. 329.) 



