436 ELMER L. SHAFFER. 



perinuclear zone to the periphery of the cell continues, until in 

 the older oocytes all the mitochondria have been localized in the 

 cortical region of the oocyte (Fig. 47). A similar centrifugal 

 migration of the mitochondria from the perinuclear zone toward 

 the cell periphery has been described by Payne ('16) in the 

 oocytes of Gryllotalpa, by Faure-Fremiet ('08) in the oocytes of 

 Julus, by Govaerts ('13) in the oocytes of the beetles Trichiosoma 

 and Cicindella, and by many other workers w r ho have studied 

 the mitochondria in the oocytes. 



At this time the cytoplasm of the oocyte is of a hyaline, homo- 

 geneous appearance, except for the mitochondrial granules located 

 in the peripheral zone. In somewhat older oocytes (in which 

 yolk-spherules have not as yet formed) numerous vacuoles appear 

 in the cortical zone of the cytoplasm where the mitochondria 

 are located. These vacuoles are at first very small in size and 

 within them can be seen the mitochondrial granules. That the 

 granules in the vacuoles are actually mitochondria is proved by 

 the fact that they respond to all the specific stains and are only 

 found in material which has been fixed according to the mito- 

 chondrial technique. The further history of the mitochondria 

 and the vacuoles of the cortical layer is concerned with the 

 process of formation of the yolk-spherules. The mitochondria 

 within the vacuoles begin to disintegrate, often showing small 

 vacuoles within themselves. At this time the vacuoles containing 

 the disintegrated mitochondria appear very much like numerous 

 small nuclei. These structures are no doubt similar to the 

 "pseudo-nuclei" of Blochmann. Korschelt ('89) has described 

 similar "pseudo-nuclei" in the oocytes of several insects, and 

 he considers them as follicle-cell nuclei which have migrated into 

 the oocyte much as the test-cells of the Ascidians migrate into 

 the oocyte to aid in the elaboration of nutrient materials. 

 Hegner ('15) has studied similar "secondary nuclei" in the 

 oocytes of Camponotus (Hymenoptera) and has also given a 

 satisfactory review of the literature dealing with these structures. 

 However, he is of the opinion that the "secondary nuclei" arise 

 as buddings from the oocyte nucleus and that this process is, 

 hence, comparable to chromatin diminution processes in other 

 forms (e.g., Miaslor, Ascaris). Hegner finds that the "secondary 



