348 KING. 



EXPLANATION OF PLATE XXX. 



Fig. 29. Vertical section through an egg from the body cavity. The first 

 polar spindle occupies a radial position at the surface of the egg directly under 

 the black pole. The chromosomes are arranged at the equator of the spindle. 

 Zeiss apoc. 2 mm., Oc. 4. 



Fig. 30. Vertical section through an egg from the body cavity at a stage pre- 

 ceding that of Fig. 29. ZP, Zona pellucida ; YM, inner yolk-membrane. Zeiss 

 apoc. 2 mm., Oc. 4. 



Fig. 31. Next section in the same egg as Fig. 30. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 32. Vertical section through an egg from the upper part of the oviduct. 

 Anaphase of the first polar spindle. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 33. Section through an egg from the middle part of the oviduct. Cutting 

 off of the first polar body. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 34. Vertical section through an egg from the lower part of the oviduct. 

 The second polar spindle lies at the periphery with its chromosomes arranged at 

 the equatorial plate. Zeiss, apoc. 2 mm., Oc. 4. 



Fig. 35. Vertical section through an egg from the lower part of the oviduct. 

 Separation of the sister chromosomes which were apparently fused in the first polar 

 spindle. PB, first polar body. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 36. Next section to the preceding. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 37. Horizontal section through an egg from the lower part of the oviduct, 

 showing the first polar body and the equatorial plate of the second polar spindle. 

 Zeiss apoc. 2 mm., Oc. 4. 



Fig. 38. Vertical section through a newly fertilized egg, showing the late ana- 

 phase of the second polar spindle. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 39. Section of a newly fertilized egg, showing the second polar body. 

 Zeiss apoc. 2 mm., Oc. 4. 



Fig. 40. The chromosomes remaining in the egg after the cutting off of the 

 second polar body preparing to form the female pronucleus. Next section in the 

 same egg as Fig. 39. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 41. The spermatozoon of Bufo lentiginosus. A, apex ; H, head stained 

 black with iron-haematoxylin ; M, middle-piece; T, tail. Zeiss apoc. 2 mm., Oc. 8. 



Fig. 42. Depression in the surface of an egg caused by the entrance of the 

 spermatozoon. There has been an extrusion of egg-plasm at this point to form an 

 " entrance cone." Zeiss apoc. 2 mm., Oc. 4. 



Fig. 43. Penetration of the spermatozoon into the egg and the formation of 

 the astrosphere at its anterior end. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 44. The sperm-head after it has entered the egg breaking up into rounded 

 chromatin granules preparatory to the formation of the male pronucleus. The 

 astrosphere has become decidedly oblong and a radiation marked by pigment 

 granules is forming around it. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 45. The middle-piece and tail of the spermatozoon after their entrance 

 into the egg. Zeiss apoc. 2 mm., Oc. 4. 



Fig. 46. Vertical section through an egg about one-half an hour after fertili- 

 zation. A pigment trail marks the path taken by the spermatozoon in the egg. 

 Zeiss AA., Oc. 2. 



Fig. 47. Division of the astrosphere into two parts, each surrounded by a pro- 

 nounced radiation marked by rows of pigment granules. Zeiss apoc. 2 mm., 

 Oc. 4. 



