IO6 EDWARD DRANE CRABB. 



PLATE 5. 



FIGS. 38-43 were reproduced to the scale of 0.03 mm.; Figs. 47-51, 0.02 

 mm. as shown in the plate. 



FIGS. 38, 40. Two consecutive sections showing reduction in number of 

 karyomeres of the pronuclei. Both sperm and egg pronuclei are repre- 

 sented. The polar periphery of the egg is represented by a line. Modified 

 Flemming, 6 M, iron-haematoxylin. 



FIG. 39. From a single section showing sperm and egg pronuclei with 

 two unresolved karyomeres. The polar periphery of the egg is represented 

 by a line. Modified Flemming, 6 M, iron-hsematoxylin. 



FIG. 41. From an oblique section through the definitive sperm and egg 

 pronuclei ; complete except that a part of the upper pronucleus is on the next 

 section. The pronuclei are closely appressed but are not fused. Modified 

 Burkhardt 48 C., IOM, iron-haematoxylin, Gage's acid fuchsin. 



FIGS. 42, 43. Two consecutive sections of the first cleavage nucleus. 

 Only a few astral rays show in the first section. However, I supplied the 

 amphiaster to assist in explaining both figures. Numerous chromomeres are 

 retained in the second polocyte, and the astral rays are breaking down the 

 nuclear membrane. Technique as in Fig. 41. 



FIG. 44. A sperm pronucleus from the sperm receptacle, much enlarged. 

 Modified Burkhardt 50 C., 6 M. iron-haematoxylin. 



FIG. 45. A nearly ripe ovarian ovum. Al, Ancel's layer. Projected with 

 " Zeichenokkular." 



FIG. 46. A very recently freed ovum lying in an acinus and still retaining 

 more than half of its hyaline membrane, HM. and its germinal vesicle. 

 Projected with " Zeichenokkular." 



FIG. 47. Reconstructed from two consecutive sections of a primary oocyte 

 which was deposited in the sperm receptacle during copulation. Modified 

 Flemming, 8 M, iron-haematoxylin. 



FIGS. 48, 50. Early equatorial plates of the first maturation in virgin eggs. 

 Each figure was drawn from a single section and comprises 16 and 20 

 chromosomes each. These eggs were fixed while being oviposited. 

 Modified Flemming, 6 M, iron-haematoxylin. 



FIG. 49. First maturation spindle in an egg from the same egg-mass as 

 Figs. 48 and 50, but earlier. The entire figure is on one section. The 

 number of chromosomes cannot be determined. 



FIG. 51. Very late anaphase of the first maturation division. The bulg- 

 ing first polocyte is indicated by a line. Modified Flemming 65 C., 6 M, 

 iron-haematoxylin. 



