674 THE AMERICAN NATURALIST. [Vol. XXXVII. 



of the nucleolus and after the division of the latter it also 

 divides (Fig. 5). In the elongation, constriction and division of 

 the nucleolus into equal parts and in the presence of this clear 

 peripheral layer which also elongates and divides, the nucleolus 

 in the follicle cells of the cricket is very unlike ordinary nucleoli, 

 while in both of these respects it resembles an intranuclear cen- 

 trosome or " centro-nucleolus." W hether this resemblance is 

 merely a superficial one without significance (analogy) or a fun- 

 damental likeness (homology) cannot be affirmed without a more 

 extensive study of the structures in question, particularly of the 

 fate of the centrosomes which are found in the mitotic divisions 

 in the upper portions of the tube. If it should turn out that 

 these nucleoli are really comparable to centrosomes their peculiar 

 structure and form of division would find a ready explanation. 



The biological significance of amitosis in this case cannot be 

 a matter of much doubt. These amitotic divisions are found 

 only in the terminal segments of the ovarial tubes at which time 

 the follicle cells are actively secreting the chorion (Fig. 7). 

 After the formation of the chorion and before the egg is laid 

 these cells completely degenerate and disappear. A follicle cell 

 which has once divided by amitosis never again divides mitoti- 

 cally ; in fact no mitoses are ever found in this terminal section 

 of the tube. These fails all indicate that the amitotic division 

 is, in this case, one of the last functions of these cells and that 

 it is therefore an accompaniment of cellular senescence and 



