24 C. M. CHILD. 



early stages of cytolytic gradients. Although complete series of 

 data up to the first hydranth were obtained with cytolysis, with re- 

 duction and with differential staining, complete series of figures 

 for the various methods are believed to be quite unnecessary 

 since the results of all agree. The small arrows in Figs. 10-17 

 indicate the direction in which further progress of reduction or 

 cytolysis occurs. As regards Figs. 10-12 it should also be noted 

 that the shaded portions represent those regions in which the color 

 resulting from reduction of KMnO 4 is deepest. All portions of 



FIGS. 9-1 1. 



the egg or later stage become diffuse yellow in permanganate 

 within a few moments, but the differential staining of different 

 regions becomes more and more distinct as reduction proceeds, 

 until the increasing opacity obscures the differences and dehydra- 

 tion and clearing are necessary to make them visible. 



The growing oocytes of Phialidium form a more or less regu- 

 lar columnar epithelium in the gonad (Fig. 9), each cell being 

 attached by its inner end (&) adjoining the radial canal, while 

 the superficial free pole (a) is separated from the sea water only 

 by a very delicate membrane covering the gonad. Except in very 

 early oocytes, the nucleus lies nearer the free pole. Growing 

 oocytes of various stages, isolated by teasing, rapidly assume 

 rounded form and the nucleus often breaks down or is extruded, 

 but the region of attachment remains distinguishable and serves 

 as a landmark. Such isolated oocytes show uniformly a gradient 

 in susceptibility with all agents used, in reduction of permanganate 

 and in differential staining, the cytolysis or change in aggregation 

 of the cytoplasm, the reduction and the staining beginning at the 

 free pole and progressing toward the attached pole, as indicated 

 in Figs. 10 and 11. Nucleated and non-nucleated egg fragments 

 also show a gradient which is doubtless identical with that of the 



