GLANDULAR CELLS OF THE FROG'S PANCREAS 369 



3. Genesis. Historical. There is considerable difference of 

 opinion as to the genesis of mitochondria, which may be sum- 

 marized as follows: 1) Benda, Meves ('08, '10), Duesberg ('08, 

 '10), Hoven ('10), and others claim that mitochondria are plas- 

 mic structures derived from those of the male and female sex 

 cell, and transmitted from generation to generation. According 

 to this theory they are not derived from the nucleus. 2) Mito- 

 chondria are mere products of differentiation of the cytoplasm, 

 as described by Lams ('06) and Vejdowsky ('07). The former 

 author believes that the mitochondrial granules of the egg-cell of 

 Rana temporaria are elaborated under the direction of the at- 

 traction sphere; Vejdowsky also claims that they are formed by 

 the regressive transformation of the centroplasm, as products of 

 the formative activity of the centriole. 3) Russo ('08, '10) and 

 Comes ('13) are of the opinion that mitochondria are paraplasmic 

 structures drawn in from the outside. The authors were led to 

 this assumption from observations that the mitochondrial sub- 

 stance in the egg-cell is increased by excessive nutrition or 

 by a certain food (lecithin), whereas they decrease in the 

 fasting. 4) There are some who accept the derivation of the 

 mitochondrial substance from the nucleus. Goldschmidt ('04) 

 believes to have found chromidia, first described by R. Hertwig, 

 in various somatic cells of Ascaris, and identifies them with the 

 mitochondria. According to this author, the chromatin sub- 

 stance of the nucleus consists of two components — idiochroma- 

 tin and trophochromatin. The former remains behind in the 

 nucleus, the latter passes over into the cytoplasm. To the 

 category of trophochromatin belongs the chromidial or mitochon- 

 drial substance. On the other hand, Wassilieff ('07) found that 

 deeply staining chromatin substance passes out of the nuclei of 

 spermatogonia of Blatta germanica, giving rise to mitochondria; 

 while Jordan ('12) is of the opinion that mitochondria are de- 

 rived from the cast-off fragments of chromosomes in the mitosis 

 of spermatogonia of the bat. Very recently, Alexeieff ('17) be- 

 lieves to have substantiated the nuclear origin of mitochondria. 



The mitochondrial filaments or chondriocontes in the secret- 

 ing pancreas cells must be multiplied in some way or other; for, 



