26 CALIFORNIA ACADEMY OF SCIENCES. 



clear matter in one spot outside of the original nucleus. 

 When the nuclear matter is evenly distributed, the same 

 power of attraction which caused the adult to divide 

 causes the sporoblasts to form, which latter is accom- 

 plished by the even grouping of the cytospheres around 

 the secondary nuclei. A thin membrane is formed around 

 the sporoblasts, after which the nucleus of the latter be- 

 gins again to divide by mitosis. 



This budding or amitosis of the nucleus has previously 

 been observed in a large variety of cells, and the various 

 views of respective investigators of this subject have been 

 set forth by Dr. Richard Zander (4) with great clearness. 

 The type of division found in the early sporogonial stage 

 of Spermatobium must, with some allowance, be consid- 

 ered as related to Arnold's "fragmentation" type, though 

 want of access to his paper (3) has prevented me from 

 making a closer comparison. 



Ziegler (5) holds that amitosis only takes place in me- 

 ganuclei, and that these soon perish after the process is 

 over. This is exactly the case with the macronucleus of 

 Spermatobium. Fritz Schaudinn (6) again has described 

 amitosis in the nucleus of various foraminifera, but this 

 process, as observed by him, differs from the amitosis of 

 Spermatobium through the presence of achromatic fila- 

 ments which divide the caryosomic substance in various 

 parts. Here then the division takes place inside the nu- 

 clear membrane, while in Spermatobium the amitosis is 

 entirely extra nuclear or outside of the original nuclear 

 membrane. 



The amitotic division of the nucleus can thus take 

 place in at least four different ways : 



Segmentation. The nucleus divides itself in equal 

 parts in the equatorial plane. 



Fragmentation. The nucleus is beaded off in various 



