Bigelow. — Nuclear Cycle of Gonionemus murbachii. 



PLATE 3. 

 All figures are from isolated cells, and are magnified 2600 diameters. 



Fig. 32. Anaphase of last spermatogonial division. The cell has been partly 

 crushed so that the chromosomes are separated and show their 

 constricted form. 



Fig. 33, a. " Resting " stage of spermatogonium. 



b. Anaphase. Stout interzonal filaments connect the daughter plates. 



Fig. 34, a and 6. Each a polar view of the daughter plate of a spermatogonial 

 division. 



Fig. 35. Late anaphase. The interzonal filaments are stout. The chromosomes 

 are densely compacted. 



Fig. 36. Still later stage. The chromosomes commence to move apart. The 

 centrosomes have disappeared. 



Fig. 37. Telophase. The chromosomes have become connected into an irregular 

 network. The interzonal bridge still persists. 



Fig. 38. Later telophase. The chromatin networks have commenced to become 

 diffuse. 



Fig. 39. Still later stage. The nucleolus is now visible in each daughter cell. 



Fig. 40. "Resting" stage of primary spermatocyte. The nucleolus is a homogene- 

 ous body. The cytoplasm of the right-hand cell contains a metaplas- 

 mic mass. 



Fig. 41. " Resting" stage of primary spermatocyte with two nucleoli. 



Figs. 42-44. Stages in the prophase of primary spermatocyte. The nucleolus 

 breaks down, and the karyosomes increase in size. 



Figs. 45, 46. Later stages. The karyosomes become condensed to form the chro- 

 matin reticulum. 



Fig. 47. Chromatin segment stage. The strands of the net are dense and 

 homogeneous. 



Figs. 48, 40. Chromatin net stage, showing different degrees of contraction. 



Figs. 50-54. Various stages in the prophase of the primary spermatocyte, showing 

 contraction phases. 



