236 BYRNES. 



EXPLANATION OF PLATE XIL 



All figures drawn with camera and lenses of Zeiss. Homogeneous immersion, 

 I J mm. apochromatic compensation, ocular 4. X dbj. 



Fig. 21 a. Egg-astrosphaere after extrusion of second polar body. The astral 

 rays are straight. 



Fig. 21 b and c. Two successive sections through the sperm-nucleus, which 

 is surrounded by rays of a spiral aster. 



Fig. 22. Egg-nucleus and spiral-aster after extrusion of second polar-globule. 

 The centrosphere consists of a deeply staining center surrounded by a light 

 peripheral zone. 



Fig. 23. Section through equator of egg containing spiral-aster. Section seen 

 from upper pole. Astral rays bent to right. 



Fig. 24 a. Section through egg-nucleus and part of astrosphaere. 



Fig. 24 b. Second polar globule and " Zwischenkorper " of Fig. 24 a. 



Fig. 25. Centrosphere and astral rays of Fig. 24 a. Homogeneous body in 

 center of clear zone which is traversed by a reticulum. The reticulum is formed 

 from inner ends of astral rays. 



Figs. 26 and 27. Sections through egg-centrosphere showing successive 

 stages in the breaking down of the central body. 



Fig. 28. Section through the reticulated egg-centrosphere after the disappear- 

 ance of the central body. The sperm-nucleus and the egg-nucleus are the same 

 size. Egg-nucleus at the upper pole. 



Figs. 29 and 30. Successive stages in the disappearance of the egg-astro- 

 sphaere. 



Figs. 31 and 32. Sections through the egg- and sperm-nucleus. The egg- 

 nucleus lies nearer the upper pole of the egg. Fig. 31 still shows indications of 

 the astral rays. 



Figs. 33 and 34. First appearance of the sperm-asters after the nuclei have 

 reached their maximum size and have come into contact with each other. 



Fig. 35. Radial arrangement of chromatin within the nuclear membrane. 



Figs. 36 and 37. Section showing closer contact of asters with sperm-nucleus 

 than with egg-nucleus. Formation of segmentation spindle. 



Fig. 38. Formation of segmentation spindle between egg- and sperm-nuclei. 



Fig. 39. Deep-staining granule (chromatin ?) in the cytoplasm near the 

 nucleus. 



Fig. 40. Mature spermatozoon. 



Figs. 41 and 42. Sections through an abnormal egg in which the apposition 

 of the egg- and sperm-nuclei occurred five hours after the eggs were laid. 



Fig. 41. Section through periphery of sperm-nucleus on side away from egg- 

 nucleus. The sperm-nucleus is accompanied by two refractive bodies (centro- 

 somes ?). 



Fig. 42. Section through egg- and sperm-nuclei. Egg-nucleus at upper pole 

 of egg near the second poiar globule. 



Fig. 43. Sperm with deeply staining bodies at periphery of egg. 



