62 PETER OKKELBERG 



nucleus on the side toward which the contraction figure is formed^ 

 but this was taken to be the vitelhne body since it may often be 

 found in other parts of the cells. No distinct centrosome or 

 attraction sphere could be found in the cells at this time. Jor- 

 gensen ('10) figures a very distinct astrosphere during the bou- 

 quet stage in Proteus, but he was not certain of the presence of 

 a centrosome. He also found that during this period there was 

 an extrusion of chromatin material from the nucleus into the 

 cytoplasm on the side next to the astrosphere. This was not 

 found to be the case in the lamprey, in which the nuclear mem- 

 brane appears to be intact throughout the period of transforma- 

 tion of the germ cells into growing oocytes. No centrosome 

 was found by King ('08) in the germ cells of the toad during the 

 synapsis period, and she concludes that probably the egg cen- 

 trosome disappears after the last oogonial division. Lams ('07), 

 on the other hand, observed a centrosome in the germ cells of 

 the frog during the bouquet stage. 



Although no centrosomes or astrospheres were found during 

 the synapsis phase in the oocytes of the lamprey, they are not 

 permanently lost, for they reappear somewhat later in the grow- 

 ing oocyte. It is probable that special technique might make 

 them visible also during the synapsis stages. Jorgensen holds 

 that the centrosome is functional in connection with the con- 

 vergence of the chromosomes along one side of the nucleus during 

 the bouquet stage, with the radiations in the cytoplasm through 

 the orientation of plasma inclusions, and with the formation of 

 a permeable region in the nuclear membrane where chromatin 

 bodies may be extruded from the nucleus. In the lamprey no 

 extrusion of visible chromatin material from the nucleus at this 

 stage has been observed, but there is ample evidence that such 

 extrusion takes place in the dictyate stage, although there appears 

 to be no special area of the nuclear membrane over which it 

 occurs. 



It has been shown that two nucleoli are present in the germ 

 cells of the lamprey during the multiplication period. During 

 mitosis these are reduced to one, which also later disappears. 

 In the resting cells after mitosis a single nucleolus appears and 



