64 CYTOPLASMIC STRUCTURES IN THE SEMINAL EPITHELIUM OF THE OPOSSUM. 



forerunners of the mitochondria," it should be noted that they are already deprived 

 of their main interest, since it has been established that chondriosomes are present 

 in all preceding stages. A special effort, however, was made to ascertain what 

 they could be. It appears probable that the nuclear condition to which Jordan 

 refers is the appearance one constantly finds at the periphery of pieces fixed with 

 reagents containing osmic acid; in fact, the typical image of a nucleus after strong 

 osmication, as shown in figure 5. That the masses of chromatin there represented 

 are expelled into the protoplasm is an assumption in favor of which no evidence 

 could be found. 



There is little to say regarding the behavior of the chondriosomes during 

 the mitoses of maturation. The process is similar to what has been described in 

 other mammals, and identical in both divisions, so that it appeared useless 

 to give more illustrations than figure 6, which represents the metaphase of the 

 first division. The chondriosomes are found all over the cell. Later they occupy 

 the space between the daughter-nuclei and are segregated in equal quantities, or 

 approximately so, between the daughter-cells. 



SPERMIOGENESIS. 



FIRST PERIOD. 



The chondriosomes of the young spermatid have still a filamentous form (figs. 

 7 and 8) . Immediately after the stage represented in figure 8 in Benda's prepara- 

 tions, and still a little later after Regaud's fixation (see figure 17, which represents 

 a somewhat more advanced stage than figure 8), one finds only small vesicles, 

 elongated at first (fig. 9), later perfectly spherical. These vesicles have been 

 observed by Jordan. As it is well known that chondriosomes when poorly pre- 

 served have a tendency to swell, the interpretation suggested itself that this appear- 

 ance was due to defective fixation, notwithstanding that during the interval between 

 the end of the first period and the beginning of the second no other form of chon- 

 driosomes was found in fixed material. The study of living cells confirms this view; 

 such stages as are represented by figure 9 are readily recognizable in teased prepara- 

 tions of seminiferous tubules, and no vesicles (only solid granules) can be seen in 

 them. It is a fact, however, that during this particular period the chondriosomes 

 are especially sensitive to the action of fixing reagents. At the same time they 

 acquire a considerable power of resistance to the dissolving action of acetic acid. 

 From this time on they can be found in nearly any material. I have seen them in 

 pieces fixed with Flemming's, Benin's, or Hermann's fluids, all of which hold 5 per 

 cent acetic acid. They do not, however, appear quite so clearly as in Benda's or 

 Regaud's preparations and, furthermore, they retain a swollen appearance even 

 in these later stages, during which, in Benda's or Regaud's material, they reappear 

 as solid granules or rods. This increase in the resistance on the part of the chon- 

 driosomes to acetic acid in the last stages of spermiogenesis is nothing new and 

 seems to be of general occurrence. Only lately (1918) I described another instance 

 of it in the testicle of Fundulus. It is worth while, however, to emphasize it in this 



