THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. 123 



chondria to be composed, are able, outside the body, to pick up, condense, and 

 concentrate urea. We desire further information on these and other points before 

 passing tentative judgment on the possible role of niitochondria. 



FATS. 



The relation between vitellus, neutral fat, lipoid, and myelin droplets and 

 mitochondria is undoubtedly very intimate, for we have good reason to suppose 

 that mitochondria are themselves, at least in part, phosphatids, and phosphatids 

 are made up of phosphoric acid, fatty acid, glycerol, and some nitrogenous base 

 like chohn. The exact chemical relationship of yolk spherules to ovovitellin is 

 little understood, but it seems clear that, though ovovitellin is more of the nature 

 of a nucleoalbumin, it contains, nevertheless, a large amount, some say as much 

 as 25 per cent, of the phosphatid lecithin. In recent years interest has become 

 focussed on these phosphorized hpoids and there is an ever-growing demand for 

 accurate information regarding them. The difficulties presented to those who 

 attempt to study them within individual cells are verj' obvious and should be 

 kept in mind during the subsequent discussion. 



There are indications in the oogenesis of almost all organisms which may be 

 taken to mean that the mitochondria are either partially or totally transformed 

 into deutoplasmic substances, hkc vitellus. The same is true in certain cases of 

 spermatogenesis where the male sex-cells are very large, approaching the eggs in 

 structure. The relation between mitochondria and vitelline granules has also 

 been studied in amphibian embryos undergoing metamorphosis. 



The oft-cited observations of Loyez (1909, p. 191) are generally regarded as 

 constituting the most con\'incing evidence of the direct transformation of mito- 

 chondria into vitelline globules. She was able to distinguish the following stages 

 in the development of the eggs of Ciona intestinalis: (1) in the youngest oocytes 

 only a few granulations may be seen about the germinative vesicle and in the periph- 

 eral cytoplasm; (2) in a more advanced stage the mitochondria are disposed in 

 linear series, in strings, throughout the cytoplasm; (3) the individual mitochondria 

 become spherical, increase in size, and in their interior present a central and clearer 

 area. Finally these globules fuse together, increase still further in size, and be- 

 come the definitive vitelline sjiheres. She remarks, further, that in other closely 

 related ascidians, like Cynthia tetraedra and Cynthia morus, the vitelline globules 

 are not formed from mitochondria, but arise quite independently from them. 

 These results are partially confirmed by Govaerts (1913, j). 415), working with 

 insects, but he has not been able to demonstrate a direct transformation of mito- 

 chondria into vitelline spherules. 



The clumping of mitochondria and their fusion to form fatty masses which 

 enter into the composition of the vitellus have been described by Henneguy in the 

 oogenesis of Pynhorcis apterus, and by Faure-Fremiet (1910a, p. 548) in both the 

 oogenesis and the s[)ermatogenesis of Lithobius forficatus, but they do not specify 

 the properties of the said fatty masses. 



