196 ^ CYTOLOGY 



CHAP. 



acetic acid, their non-chromatic nature is made especially evident, since 

 in their usual condition chondriosomes are dissolved, or at any rate 

 caused to disappear, by this reagent, which on the contrary forms one 

 of the commonest and most useful of chromatin fixatives. Largely for 

 this reason, doubtless, chondriosomes do not often appear in cytological 

 figures, which are mostly taken from material which has been fixed 

 with regard to the preservation of the nuclear structures. Chondriosomes 

 are readily seen, and their movements followed in detail, in living cells 

 (see, for example, Lewis and Robertson, 1916). 



Meves (1910) identifies the chondriosomes with the filaments of 

 Flemming (except that the latter included certain structures under this 

 term, such as the fibres of the achromatic figure, which appear to be 

 of a different nature) and with the granules of Altmann. 



That the chondriosomes possess a peculiar significance in morpho- 

 genesis and heredity is based on the following claims : 



(i) They are permanent cell structures, persisting from one cell 

 generation to another, reproducing themselves by fission. 



(2) There are indications that in some cases arrangements exist for at 

 any rate an approximately equal partition of the chondriosomes between 

 two daughter cells at cell division. 



(3) They are carried into the egg by the spermatozoon at fertilization. 



(4) The chondriosomes found in the fertiUzed egg can be traced in 

 the tissues of the developing embryo, and have been described as actually 

 giving rise to permanent cell structures of the adult — for example, 

 neurofibrillae, muscle fibrillae of striated muscle fibres (Meves, 1908 ; 

 Duesberg, 1910) and to various organs of plant cells (see Meves, 1918). 



It must suffice to comment very briefly on these four points. 



(i) Since the chondriosomes lie in the cytoplasm, and since the 

 cytoplasm of the mother cell is divided among the two daughter cells, 

 it follows that the chondriosomes also must be passed on from cell to 

 cell ; the spermatogenesis of Blatta illustrates this (Fig. 29). There is 

 no e\ddence, however, to show that they may not disappear and re-form 

 in the cytoplasm from time to time ; their origin de novo in the cytoplasm 

 has indeed been described in certain cases (Schaxel, 1912 ; Beckwith, 

 1914), while evidence of their regular multiplication by fission is practi- 

 cally non-existent. 



(2) So far very Httle evidence exists for this, though at cell div'ision 

 the chondriosomes are often doubtless distributed together with the 

 cytoplasm into two approximately equal masses. On the other hand, 

 certain cases have been described where the division is unequal. This 

 is manifestly the case in the polar body formation, where practically 

 the entire mass of the chondriosomes of the oocyte L are left in the ripe 

 egg, exhibiting nothing corresponding to the reduction of chromosomes. 



