Existence of Cell Communications between Blastomeres. 499 



a light cover glass supported at its four corners by means of wax feet, over a 

 few eggs in a drop of sea water on a slide, it is possible to hold the eggs in 

 any position, and study them if necessary for hours under an oil immersion 

 lens. By pressing down the cover glass, the eggs can be flattened slightly 

 without causing any serious injury or displacement of the cells. It is 

 then possible to closely examine the interior of the blastocoel. In prepara- 

 tions of this kind, delicate strands can be seen in some cases connecting 

 the blastomeres, their appearance being much the same as in fixed material 

 with the exception that they are less granular and finer in appearance. 

 Unfortunately this method of examination may be held to cause their 

 formation. 



The fixation of the sections from which the accompanying drawings 

 (Plate 18) were made was in all cases good, Flemming, Hermann's fluid, or 

 Corrosive-acetic being used.* The sections were cut in the ordinary 

 way in paraffin ; very dilute paracarmine being used as a stain. 



Fig. 1, is taken from a section of an egg of Eupomatus, three hours after 

 fertilisation, and fixed with Flemming's strong solution. A fine strand of 

 protoplasm is seen connecting one blastomere with another across the 

 segmentation cavity. The granules of the protoplasm of one cell, are trace- 

 able without break in continuity throughout the course of this strand, into 

 that of the other. By examining the consecutive sections through this egg, 

 it can be readily determined that this strand does not represent a ridge on 

 the wall of the cavity so cut as to appear as a strand in the section. It is 

 quite plainly in the middle of the cavity, running freely from one wall to the 

 other. In this and the subsequent sections the darkly staining egg membrane 

 is seen surrounding the egg, and is remarkable in Eupomatus for its thickness, 

 remaining about the egg till a relatively late stage in development. 



Fig. 2, is also taken from a Eupomatus egg, some four hours after fertilisa- 

 tion fixed in Flemming's solution. Here several strands are seen irregularly 

 crossing the cavity, one strand being shown cut across in the section. In 

 the cavity a number of granules are seen. 



Fig. 3, is from an egg somewhat similar to that from which the last 

 section is taken. In one of the cells a conspicuous mitotic spindle is 

 shown cut across. The large cells (marked en in the figure) on the lower 

 side of the section subsequently become the entomeres, while the dorsal cells 

 with which they connect, become the " apical rosette " cells, which are plainly 



* It is worthy of note that "Wilson (17), in comparing the appearance of living with 

 fixed protoplasm, comes to the conclusion that its treatment with suitable reagents "does 

 not materially distort or pervert the normal structure, but gives on the whole a remark- 

 ably faithful picture of the structure existing in life," (p. 5). 



