232 Chas. W. and G. T. Hargitt. 



the ovary, and that fertUization takes place a little later in the 

 gastric cavity. 



The material obtained from Cyanea does not permit the deter- 

 mination of the cytologic details of the maturation process nor of 

 fertilization. But it was found that two polar bodies were formed 

 one of which sometimes divided again. The polar bodies are of con- 

 siderable size, relatively larger than polar bodies in the Hydro- 

 medusse. The chromatin is usually enclosed within a membrane, 

 but is collected into several more or less distinct masses, not form- 

 ing a reticulum. The polar bodies remain attached to the eggs for 

 varying periods, being occasionally found in blastulse, though they 

 commonly disappeared soon after the beginning of cleavage, prob- 

 ably through the rupture of the delicate egg membrane. 



Cleavage 



The first division of the egg is meridional, the cleavage plane 

 in some cases (figs. 1, 4) being almost co-incident with the plane 

 of the polar axis, while in other cases (fig. 11) there was consider- 

 able divergence between these two planes. There result two cells 

 which are nearly equal in size (figs. 1, 3, 4), though rarely exactly 

 so, and in a good many cases there is a marked inequality (fig. 2) 

 one blastomere being perhaps only about half the size of the other. 

 This irregularity is also quite marked in the cleavage of Aurelia. 

 It can be followed without difficulty in the living egg, and one 

 finds upon looking over a series that a considerable number exhibit 

 this feature, not only in the size of the blastomeres, but in their 

 arrangement also. 



When the first division is completed there is often present a 

 small space between the blastomeres (fig. 12). This can be seen 

 in entire eggs as well as in sections, and while not present in all 

 eggs it persists, when present, to become a part of the large cleav- 

 age cavity. This early appearance of the cleavage cavity, not de- 

 scribed by earlier workers, Conklin (1908) found to be also charac- 

 teristic of Linerges mercurius.^ He found among the organized sub- 

 it may be doubted whether any such significance attaches to the cleavage 

 cavity, as was earlier assumed, or whether the space referred to in the two 

 cell stage can rightly be so regarded. — C. W. H. 



