304 FERNANDUS PAYNE 



of origin of the axis cylinder is now double, and the two parts 

 are larger and unequal in size (plate 2, J, K). The mitochondrial 

 mass still continues to elongate. Viewed from the side, the 

 stage shown in plate 3, A, appears as in plate 3, B. At this time 

 the mitochondria in cross section appear as two cylinders (plate 

 3, G) between which lies the axis cylinder. What force brings 

 these two structures into this intimate relation, I do not know. 

 In plate 3, A, the mitochondrial mass is seen to be larger near 

 the nucleus. This condition changes, either by a constriction 

 of the mass at this point or by its backward movement, after 

 which the mitochondria appear as rows of granules along the 

 axis cylinder (plate 3, E, F). 



The nuclear material has also been changing. From a loose 

 network (plate 3, A), the chromatin has condensed until all 

 traces of a network has been lost (plate 3, F). It will be noticed 

 in this figure that the chromatin is denser at the periphery of 

 the nucleus. This statement holds good for all later stages of 

 condensation until the mature spermatozoon is reached. Fol- 

 lowing the stage shown in plate 3, F, the mitochondria lose their 

 identity. Even the axis cylinder can no longer be seen. The 

 tail appears to be made up of a homogeneous substance (plate 

 3, M to Q). Whether this disappearance of the mitochondria 

 means a complete change or simply a condensation into a homo- 

 geneous mass, very much as the chromatin condenses in the 

 transformation of the nucleus, I am unable to say. 



B. In the female sex cells 



The mitochondria in the male cells have been traced from the 

 spermatogonia through the various stages of maturation into the 

 tail of the spermatozoon. The question of their origin was thus 

 left undetermined. This fact led me to examine the female 

 sex cells in the material already at hand. In the oogonia at 

 one side of the nucleus, there is a mass of granules similar in 

 appearance to those in the spermatogonia (plate 4, F). These 

 granules are, I believe, the mitochondria. As the cells increase 

 in size during the growth period, the mitochondria move out 



