54 Puh. Paget Sound Biol. Sta. Vol. 2, No. 34 



The figures have all been drawn with a camera lucida from preserved 

 laaterial. Figures 1 and 2 are from sections stained in iron haematoxylin ; 

 the rest from whole mounts of which figures 6, 9, 13, 17 and 20 ar^ from 

 tissue stained in acidulated Delafield's haematoxylin, the others from un- 

 stained tissue. The drawings are all X 515. The lettering of the plates 

 is mostly explained by the diagram of cell lineage. 



PLATE 12 



cap., egg capsule. 



egg n., egg nucleus. 



/. p. n., female pronucleus. 



m. p. n., male pronucleus. 



p. h., polar body 



p. n., pronucleus. 



Fig. 1. Late anaphase in polar body formation on Haminea. 



Fig. 2. Telophase in formation of second polar body. Male and 

 female pronuclei have not yet approached. The long astral rays are 

 characteristic. The arrangement of the yolk spheres indicates a cone- 

 shaped clear protoplasmic area below the polar bodies. 



Fig. 3. The resting 1 -celled stage. Male and female pronuclei 

 closely appressed. The large egg capsule is shown surrounding the egg. 

 Zonal distribution of the yolk is beginning. 



Fig. 4. The first cleavage spindle lying at right angles to the polar 

 axis. Zonal distribution marked. 



Jig. 5. Beginning of cytoplasmic cleavage. The spindle has rotated 

 to a diagonal position. 



