340 SYDNEY J. HIOKSON. 



cytoplasm. Throughout this mitosis the clear outline 

 (membrana limitans ?) is never lost. 



The mitosis of the micronuclei of Dendrocometes has con- 

 siderable i-esemblance to tbe mitosis of the micronuclei of 

 Paramoecium, as described by Hertvvig (8), of Bursaria, as 

 described by Provvazek (22), and of other Ciliata. 



The Meganucleus. 



In specimens of Dendrocometes that are neither con- 

 jugating nor preparing for gemmation, the meganucleus is 

 usually a spherical body 0'02 mm, in diameter. It is not, 

 however, constant in shape, many examples being found that 

 are oval or even spindle-shaped. 



It is usually situated in the centre of the animal's body, 

 but it is often more or less excentric. On examination in 

 section with an oil immersion lens, there may be seen a 

 distinct meshwork of darkly staining lines which appear to 

 support a series of minute rounded chromatin grauules (PI. 18, 

 fig. 14). In many cases the lines connecting these granules 

 cannot be easily seen when the appearance is as shown in 

 PI. 18, fig. 10. In the meshes of the darkly staining chromatin 

 there is a homogeneous substance, which in many iron- 

 haematoxylin preparations is quite colourless, but stains 

 faintly yellow with brazilin. 



Plate states that in the nucleus there are a number of 

 nucleoli: "Bei einem Thier meiner Praparate ist der ganze 

 Kern dicht erfullt von solchen Binnenkorperchen deren jedes 

 von einem hellen Hof umgeben ist." I have frequently seen 

 in my preparations appearances similar to this described 

 and figured by Plate, but my interpretation of them is 

 different. In the first place I must state very emphatically 

 that in my opinion there is never in the meganucleus of 

 Dendrocometes any body or bodies which correspond with the 

 nucleoli of Metazoan cells. The clear space round the ''Binnen- 

 korperchen" of Plate is in my opinion due entirely to the 

 refraction of the light in passing through the preparation ; 

 and this opinion has been thoroughly tested by comparison 



