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THE AMERICAN NATURALIST 



[Vol. XLI 



According to the more generally accepted view the terminal chamber 

 contains the undifferentiated elements from which are derived not 

 only the eggs but the nutritive cells and the cells of the follicular 

 epithelium which surrounds the developing eggs. Korschelt, who is 

 widely quoted, formerly believed that these elements might be traced 

 back still further to indifferent elements of the terminal filament. 



Sharply opposed is the view that the sex-cell is sui generis, in origin 

 entirely distinct from the surrounding epithelium. This interpreta- 

 tion has been gaining ground but is opposed by Marshall's recent 

 results. 



In view of the conflicting conclusions of previous investigators the 

 recent work of Kohler^ is of much interest. The fact that the work 

 was done under Professor Korschelt's supervision adds especial weight 

 to the author's conclusions. 



The contradictory results obtained by previous workers are due 

 mainly to the use of mature specimens, and to poor technique (staining, 

 fixation, or to thickness of sections). Kohler has studied sixteen 

 species of Hemiptera, of most of which he had immature as well as 

 mature stages. Of three species he had a series of the nymphal stages. 

 Fixation was by means of Hermann's or Zenker's fluids, as alcohol or 

 the much-used corrosive sublimate were wholly unreliable. 



It was found that the cells of the peritoneal epithelium, the termi- 

 nal filament, the epithelium of the gcrmarium and of the follicles, are 

 of common origin. These somatic cells are perfectly distinct from the 

 sex-cells and the nutritive cells which are derived from the latter. 

 The germarium is filled exclusively by the germ cells and is always 

 sharply set off from the terminal filament, usually by a distinct mem- 

 brane. There are no "free nuclei" present. 



Kohler's investigation was not confined to the question of the origin 

 of the cells but included a thorough study of the histological structure 

 of the ovaries, and an especial consideration of cell-division. He 

 found that cell-division takes place in the peritoneal epithelium, 

 terminal filament, egg-tube, and germarium and is always by mitosis. 

 On the other hand the so-called amitotic division occurring in the 

 follicular epithelium is confined to the nucleus and never leads to 

 cell-division. However, the tissue in which it occurs is not senile, 

 but living, and capable of growth and activity. Only after the nuclear 

 divisions have occurred begins the cell activity (secretion of egg-chorion) 



» Kohler, A. Untersuchungen fiber das Ovarium der Hemipteren. Zeit- 



