GERM-CELL HISTORY IN THE BROOK LAMPREY 63 



shortly afterward a second. When the cells enter the synapsis 

 phase, the nucleoli again disappear, apparently during synizesis. 

 When the cells enter the growth phase, only one nucleolus 

 appears in each cell. This remains during the whole period as a 

 very prominent spherical structure. Whatever may be the 

 function of the nucleoli, they are, as shown by their reaction to 

 stains, true plasmosomes, and not composed of chromatin mate- 

 rial. This is contrary to the idea of Lubosch ('03), who believes 

 that in the lamprey and in other forms the chromatin material is 

 stored in the nucleolus during the growth period of the egg. 

 This view is based largely on the fact that the chromosomes 

 seemingly disappear during the later stages of growth. Lubosch 

 also thinks he has evidence that the maturation chromosomes 

 are derived from the nucleolus. I have found some evidence 

 which indicates that the maturation chromosomes appear in the 

 clearer portions of the nucleus and do not come from the nucleolus. 



Von Winiwarter and Sainmont ('09) found in the nucleus of 

 the oogonia of the cat, at the time when the cells were preparing 

 for mitosis, an elongated body which stained like chromatin. 

 Often it had a horseshoe shape, and it was larger than the other 

 bodies of the nucleus. During mitosis it divided, but much 

 more slowly than the chromosomes. In the oocyte it was often 

 attached to the plasmosome, but sometimes it was free. When 

 dividing, it split longitudinally, and during the growth period 

 it disappeared. The body was supposed by the authors to be a 

 sex chromosome (monosome). Gutherz ('12) found a similar 

 body in the spermatocytes of the cat, but came to the conclusion, 

 on account of its staining reaction, that it w^as a true plasmosome 

 ''der einen Gestalt ein Heterochromosome in Herteropyknose 

 vertauscht." Gutherz doubts that the body observed by von 

 Winiwarter and Sainmont was a true sex chromosome, since no 

 differential stain was used by them. Furthermore, there should 

 be two sex chromosomes present in the oocyte of the cat, if such 

 bodies are present at all, since in this form the male is apparently 

 heterozygotic with respect to sex. 



There is considerable danger of misinterpreting nuclear bodies. 

 Many of the structures described in the germ cells of vertebrates 



JOURNAL OF MORPHOLOGY, VOL. 35, NO. 1 



