The Medusce of Millepora. 



7 



one. In this piece, however, I noticed that in one-third of the area 

 the fours were about six times as numerous as the threes, while in the 

 remaining two-thirds the threes were about nine times as numerous 

 as the fours. 



No very definite conclusions can be formed upon these figures, but it 

 seems to me probable that so little is the form of the medusa of Mille- 

 pora stereotyped, that a slight variation in the distribution of nourish- 

 ment in the canals may be the determining cause of the medusa being 

 triradiate or quadriradiate. 



Fig. 3. 



z 



The germinal vesicle of each large ovum is regularly spherical in 

 shape, ^vith a very sharp outline. The nucleoplasm is apparently 

 homogeneous, and resists the action of iron-hsematoxylin and carnune, 

 exhibiting no nucleolus nor chromatin granules. 



In addition to the large ova, there are always present in the medusa 

 several oocytes. These cells stain much more deeply than the ova, and 

 many of them exhibit a well-defined nucleus with a deeply staining 

 nucleolus. In some cases the cytoplasm of one of these cells may be 

 seen to be continuous with the cytoplasm of an ovum, and I have little 

 doubt that most of them, and perhaps all of them, are ultimately 



