242 C. O. WHITMAN. 



axis of tlie egg, are seen some fine granular lines which together 

 form a sort of spindle, the two poles of which appear to be near 

 the centres of the polar areas These lines, which are the same 

 as the inter-stellate lines before mentioned, are well defined, and, 

 in this case, more strongly expressed than the radial lines of the 

 two polar areas. The oral ring has lost the distinct outline of 

 the previous stage (fig. 71), and plunged deeper towards the 

 centre of the egg. The calotte (cal.), though small, is still 

 plain to be seen, supported by a slender column of deufoplasm. 

 The aboral ring-disc has also lost its sharp outline, and advanced 

 towards the centre of the e^sc. At the surface of this ])ole are 

 seen several highly-coloured spots, probably remains of the 

 disc. 



Fig. 77 represents a section in the plane of the ring, taken 

 about 20 mm. under the upper pole. The ring-substance is 

 here plainly more deeply coloured around the base of the 

 calotte. I have recognised this but once in transverse sections, 

 and twice in horizontal sections. 1 am unable to give any 

 farther account of it. 



Stage 73 also bears the same date as the two preceding, but is 

 evidently farther advanced than either of them. One pole of 

 the aniphiaster is seen more highly magnified in fig. 78. Tri 

 the centre of the polar area is a clear circular space (ca), around 

 the edge of which the nucleoplasm is a little more dee))ly 

 coloured, giving the appearance of a more or less well-marked 

 ring around the same. The strongly expressed radial lines end 

 in this ring, and are not to be distinguished from the spindle- 

 fibres. 



The ring substance has plunged a little deej)er, and is directed 

 towards a point to the right of the centre of the spindle. The 

 zones of protoplasm seen in previous stages about the ring-sub- 

 stance are no longer recognizable. Stage 74 is about 15 minutes 

 later than stage 73 (2 h. 45 min.). The poles of the amphiaster 

 are farther apart than in the previous stage, but are still con- 

 nected by a band of nucleoj)lasm in which no lines or fibres are 

 visible. They have become somewhat lens-shaped, with their 

 longest diameters at right angles to the axis of the amphiaster. 

 The clear central spaces (ca) seen in each polar area of stage 73 

 are replaced by central stripes. The substance of the stripes 

 appears a little coarser than the nucleoplasm, and imperfectly 

 distributed in two to four parallel lines. The radial lines are 

 very strongly expressed, extending to the periphery of the 

 egg. The ring disc of the aboral pole has taken a sagittal 

 form. Ten to fifteen minutes later (3h.) the first cleavage is 

 already in ))rogress (fig. 75). The remnants of the two rings 

 are found a little to the right of the plane of division. The 



