No. 501] 



NOTES AND LITERATURE 



617 



senting a very different account and interpretation of the process 

 of oogenesis. 



There is a stage in oogenesis, before the eggs are developed, 

 when the protoplasm forms a peripheral layer enclosing a large 

 region free from protoplasm in the interior of the oogonium. 

 Other authors have believed this region to be a space containing 

 cell sap, and developed by the gathering and flowing together of 

 vacuoles in the center of the oogonium. Claussen describes the 

 accumulation within the oogonium of a slimy substance which 

 he believes to be derived from the degeneration of the cytoplasm. 

 This cytoplasmic degeneration is conceived as proceeding out- 

 ward until finally the protoplasm lies as a relatively thin layer 

 in the form of a hollow sphere under the oogonium wall. The 

 well-known nuclear degeneration accompanies, according to 

 Claussen, that of the cytoplasm until relatively few nuclei remain 

 in the peripheral layer. This account of an extensive cyto- 

 plasmic degeneration to form a region filled with slime in a 

 living active cell is not paralleled, so far as the reviewer is aware, 

 in any cytological studies upon plants, and is likely to require 

 more detailed study of a microchemical character before it will 

 be accepted. 



Claussen is convinced in agreement with Davis that there is 

 only one mitosis in the oogonium and not two mitoses with 

 chromosome reduction as reported by Trow. This is an impor- 

 tant point, since Trow's view of chromosome reduction during 

 oogenesis is contrary to the rule among plants that the processes 

 of gametogenesis are unaccompanied by chromosome reduction. 

 The species of the Saprolegniales which are sexual probably 

 reduce the chromosome number (doubled by the fertilization of 

 the egg) with the germination of the oospore; the apogamous 

 species never have the double number, since the eggs develop 

 parthenogenetically. 



The account of nuclear structure, the mitosis, and their sig- 

 nificance for the processes of oogenesis presents a point of view 

 entirely different from both Davis and Trow. Claussen reports 

 a central body in the resting nucleus and at each pole of the 

 intranuclear spindle, lie believes that these establish a nuclear 

 structure with polar organization similar to that of Phyllactinia 

 as described by Harper (see review in the July number of the 

 Naturalist), but on account of the small size of the nucleus the 

 behavior of this central body was not studied in detail. Each 



