i8 



ATLAS OF THE FERTILIZATION AND KARYOKINESIS OF THE OVUM. 



Plate IV. Phototype i6. 



First Coniaci of the Nuclei (8 minutes). 



The central body of the aster has tiattened down against the egg-nucleus, and the two nuclei have come together 

 (cf. Text-fig. XI. B). The remains of the entrance-cone faintly appear at the upper periphery. The egg-nucleus has 

 become slightly irregular in contour and shows a number of amoeboid processes on the side toward the sperm-nucleus. 



A ' 



Fig. XI. 



Fig. XI. — Approach of the two nuclei (looo diameters). 

 .\. Five minutes after entrance. The two nuclei are rapidly approaching (both nuclei move). E, the egg-nucleus. The sperm-nucleus has already enlarged somewhat, and its 



shape has changed. C, the entrance-cone. (Phototypes 14, 15.) 

 B. Seven minutes after entrance. The sperm-aster has greatly increased in size and its central mass has come in contact with the egg-nucleus (E). The sperm-nucleus is now 



rounded, considerably enlarged, and its substance is less compact. At S, S are two sperm-nuclei lying outside the egg (cf. with that within the egg). 



The central body of the sperm-aster lies at a slightly lower level than that at which the photograph is taken, and therefore 

 does not clearly show, but the astral rays are very distinct, passing in all directions toward the periphery of the egg and 

 extending inward more or less around the egg-nucleus. 



Plate V. Phototype 17. 



First Contact of the Nuclei (6 minutes). 



This specimen, like the last, shows the first contact of the two nuclei, as well as the sperm-aster and entrance-cone. 

 It differs, however, in the much smaller size of the aster, which is scarcely larger than in No. 13. This is due (as shown 

 by observation of the living egg) to the fact that the spermatozoon has entered at a point near the excentric egg-nucleus, 

 and has therefore traversed only a short path. The aster has therefore not had time to attain its maximum size. 



Plate V. Phototype iS. 



Extension of the Aster preparatory to its Division {/o minutes). 



This figure is taken from a specimen double-stained with hjematoxylin and acid fuchsin, and is somewhat indistinct, 

 the astral rays, especially, being scarcely visible. It shows very clearly, however, the central mass of the aster (purple in 

 the section), flattened against the egg-nucleus and extending around it in the shape of a horseshoe. The comparison of 



