GAMETOGENESIS OF SACCOCIRRUS 25 



as it is morphologically derived from preceding materials 

 which stained like chromatin, will be found to stain oxyphil, 

 or in the red stain. As Bayliss especially has shown clearly 

 in his valuable ' Principles of Physiology ', staining depends 

 on a number of more or less obscure factors, and it is probably 

 injudicious to lay too much weight on the results of staining 

 fixed material. In many of the parasitic Hymenoptera the 

 egg nucleus contains a large heavily-staining nucleolus which 

 buds off fragments, which pass through the nuclear membrane 

 into the egg cytoplasm, where they form what are known as 

 secondary nuclei. With safranin and light green the nucleolus 

 of the true egg nucleus stains red, and the nuclear (chromatinic) 

 network a green colour. In the sponge Grantia the plasmosome 

 of the oocyte partly passes into the egg cytoplasm to form 

 bodies called by Jorgensen and Dendy ' chromidia ' ; I have 

 objected to the use of this term for such nucleolar fragments, 

 both because we do not know that they are chromatinic and 

 also because such ' nucleolar ' extrusions appear to be identical 

 with the mitochondria. 



We must face the facts frankly : the chromosome theorists 

 would object to the identification of ' nucleolar ' extrusions 

 as chromatinic in nature and as derived from the definitive 

 chromosomes. I have shown above that staining tests are 

 not conclusive ; several others, and also I myself, have demon- 

 strated that the secondary nuclei are derived from extruded 

 fragments which in the case of such forms as Myrme- 

 cina or Apanteles are, I believe, to be regarded as of nucleolar 

 origin. We find, therefore, that fragments of the nucleolus 

 can form a true nucleus, with nuclear membrane, linin network, 

 and nucleolus. 



Seiler (55 a) described in Lepidopterous eggs what he has 

 called a chromatin diminution process ; the polar body spindle 

 at metaphase is found to carry three groups of granules, the 

 two outer being the chromosomes which have divided and 

 are becoming separated, the middle group of granules being 

 apparently derived from the ends of the chromosomes by 

 a diminution process, well known in the somatic mitoses of 



