DEVELOPMENT OF SPERMATOBIUM. 23 



not yet in the sporogonium stage. The original nucleus 

 has partly diffused and formed two secondary nuclei, in 

 none of which, however, the nucleolus has assumed its 

 globular form. A thin division of the cytotheca is dis- 

 cernible extending from a to d, and from c towards the 

 center. 



In fig. 39 we find a partly formed sporogonium, in which 

 the division is more advanced. A number of nuclei have 

 formed, and the original nucleolus, or what is left of it, 

 is seen in a stage of division surrounded by a transparent 

 zone, probably the remains of the macronucleus. 



Fig. 40 represents an adult form, in which the division 

 is more perfect; one-half of the figure is drawn from a 

 focus set on the micronuclei and vacuoles, the left half 

 again was focused on the cytotheca showing the accumu- 

 lation of cytospheres. 



Fig. 4irt, b, c, represent one and the same individual in 

 division, focussed at different depths. In 41^ the focus 

 is on the vacuoles, in 4i<5 on the surface cytospheres and 

 in 41C on the nuclei. Fig. 41^ is a nucleus drawn on a 

 larger scale. In fig. 42 is seen a Spermatobium in divi- 

 sion, in which the left half consists of an undeveloped 

 spermatogonium, while the right part consists of two 

 separating spermatogonia, in one of which is seen re- 

 mains of a larger nucleus. 



My conclusions about the division of the adult may be 

 summed up as follows : 



1. The object of division is not the propagation of 

 the species, but rather a convenient subdivision of the 

 large forms. 



2. New macronuclei are sometimes formed in the new 

 individual, but not always. 



3. Micronuclei are always formed previous to segrega- 

 tion of the new individual. 



