INCLUSIONS IN EGG OF ECHINAEACHNIUS 473 



found could be demonstrated in the unfertilized egg, but some of 

 them changed or disappeared during subsequent stages of de- 

 velopment. Where there were progressive changes in the cleav- 

 age stages, a whole series was mounted on one slide. Thus any 

 variation due to differences in technique of staining was elimi- 

 nated, since all stages of the same series received the same 

 treatment. 



Gatenby ('19 b) and others have classified cell inclusions in two 

 main groups: first, inert inclusions like deutoplasm and, second, 

 active or living inclusions like mitochondria. As deutoplasm are 

 classed fat, glycogen, yolk, etc. The egg of Echinarachnius 

 parma contains a considerable amount of fat. The glycogen, if 

 there had been any, would have been dissolved out by the tech- 

 nique employed in preparing this material. The cytoplasm is 

 packed with spherical or plate-like bodies of nutritive material 

 which is identified as yolk. Active inclusions in the form of 

 mitochondria have been demonstrated. There is still another 

 type of structure found in these eggs. It is an inert inclusion and 

 yet is not deutoplasm. It will be considered under the heading 

 'Precipitations.' The occurrence of these substances will be 

 considered more in detail. 



A. Deutoplasmic inclusions 



1. Fat. It is known (Partington and Huntingford, '21) that 

 fat droplets reduce osmic acid to osmium dioxide and assume, 

 therefore, a dense black appearance after the use of a fixing 

 fluid containing osmic acid. Accordingly, eggs which had been 

 fixed in Fleming, Flemming without acetic, or Meves' fluid were 

 mounted unstained and examined for fat. No fat was found in 

 the material which had been fixed for seven days, but in the 

 Flemming and in the Flemming without acetic material which 

 had been fixed for eighteen to twenty-four hours there were 

 numerous black bodies. Figure 1 shows an unfertilized egg 

 fixed in Flemming without acetic and mounted unstained. There 

 are in the cytoplasm large blackened masses surrounded by fine 

 droplets of blackened material of uniform size, and in some cases 

 there are clumps of fine droplets without any central larger drop. 



