Mitochondria, Golgi Apparatus, and Yolk. 151 



In the animal egg, besides the mitochondria which have thus 

 been mistaken for chromidia, we have the Golgi apparatus. Since 

 the latter is never demonstrated in eggs, by the usual methods, we 

 do not believe that Golgi grains liave so far been misinterpreted 

 as "chromidia." The case of the male cells has already been 

 mentioned. 



It may be noted here that trus chromidia, by which we simply 

 mean granules of chromatinic nature distinct from the nucleus, 

 but traceable to nuclear activity, do occasionally occur in metazoan 

 oogenesis. The cases of insect oogenesis are well known (.?, 17) ; 

 in Hymenopterous insects especially are often found granular 

 chromatinic structures free in the cytoplasm, and quite distinct 

 from either mitochondria or Golgi apparatus. Such cases have 

 been noticed, but less well studied in other Invertebrata. It can 

 be stated that true chromidia (chromatinic) are not characteristic 

 of metazoan cells. Nearly every so-called case of the occurrence 

 of chromidia in Metazoa is really a misinterpretation of the 

 mitochondria. 



On page 153 we have given a scheme showing the fixing and 

 staining reactions of chromatinic structures, plasmosome, and of 

 the cytoplasmic inclusions such as the mitochondria. It will be 

 noted that it is possible to stain both mitochondria and true chro- 

 matinic structures in different colours in the same preparation. 

 For the modus operandi of these methods, see {11) and {18). 



The so-called Chromatin Emission during 

 Oogenesis. 



There still appears to be a rooted belief that the nucleus is able 

 to, and constantly does, pass out granular emissions of true chromatin 

 into the Qgg cytoplasm ; it is also believed, but with more justifica- 

 tion, that the nucleolus or plasmosome may pass out and break up 

 into granules which are in some way concerned with yolk forma- 

 tion. Working with inappropriate methods, and in ignorance of 

 recent researches on the cytoplasm, some observers are wont to 

 describe any basophil or even chromophil cytoplasmic granules 

 as chromidia, and to trace the origin of such granules to the 

 nucleus. 



Among more modern workers, Schaxel {37^ 38) has written a 

 great deal on these questions ; in the polychaete worm, Aricia 

 fcetida (Claparede), for instance, he describes how, during oogenesis, 

 the nuclear matter increases in bulk, and then, " When the chro- 

 matin increase has reached a certain stage, there appears, with 

 simultaneous cell growth, a dense mass of numberless chromatin 



