GROWTH OF EGGS AND EGG-STRINGS IN NEPHELIS. 209 



covered one very important feature of the archianiphiaster, 

 T^'hich these investigators appear to have entirely overlooked, 

 namely, the " spiral aster/' which Dr. Mark, of Harvard 

 University, was the first to discover in the egg of Limax 

 (No. 23, p. 494, and No, 24). 



In the eggs that are found floating in the ovarial fluid the 

 germinal vesicle has usually disappeared, and in its place a 

 bi-stellate figure — the archiamphiaster — is found (fig. 15, 

 PI. IV). In the centre of each star there is a clear space — 

 the polar area — which in hardened preparations looks finely 

 granular. The astral rays are at first rather weak, but they 

 can be made out, even in the living egg (fig. 19). The in- 

 terstellate rays appear to meet and form a more or less 

 spindle-shaped area. The spindle rays appear to differ in no 

 essential way from the other radial rays, nor do they, so far 

 as I can see, converge to a point in the centre of either pole 

 of the figure, as Hertwig represents in his figures. At this 

 time the spindle is ill defined, and measures only about '002 

 mm. in length. A thickened equatorial zone (" Kern- 

 platte," Strasburger) of the spindle is very doubtfully 

 recognisable. 



In eggs examined immediately after deposit (fig. 16) the 

 appearance of the archiamphiaster is markedly different. 

 The polar areas, however, remain without any apparent 

 change. The spindle has acquired a pretty well-defined 

 outline (ca. "03 — *035 mm. long, '013 mm. wide). A glance 

 at figs. 15 and 16 will show that in the latter the spindle 

 has not only elongated, but has become decidedly larger. 

 The spindle rays are distinct, and their thickened equatorial 

 zone is unmistakably established. But what are most in- 

 teresting are the rays of the asters. They are much bolder 

 in appearance than in eggs found floating in the ovarian fluid 

 (fig. 15). They have greatly increased in length, extending 

 almost to the surface, describitig nearly uniform curves, so 

 that they have a spiral arrangement. Fig. 16 shows this 

 spiral arrangement of both stars. Fig. 17 is an optical sec- 

 tion through the lower star in fig. 16, seen from above. The 

 rays of the two stars always curve in the same direction. 

 Dr. Mark remarks that " the spiral may be either dextralor 

 sinistral." In all my drawings, of about a dozen different 

 cases, I find the spirals of both asters dextral when the am- 

 phiaster is seen from the side. If, however, either aster is 

 viewed from above, the spiral will be sinistral. This may 

 be accounted for by supposing that the rays have a double 

 curvature. 



A few minutes after deposit, as the archiamphiaster pushes 



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