Haroitt: Pennaria tiarella and Tubularia crocea . 



PLATE 4. 



Figs. 25-28 Pennaria tiarella. Fig. 29 Tubularia crocea. 



Fig. 25a. Germ nuclei of unequal size mutually flattened. Bouin's fluid, 

 iron hematoxylin and Congo red. X 1600. 



Fig. 25b. Another section of same nuclei, showing that the concentration of 

 the chromatin begins on one side of the nuclei. X 2250. 



Fig. 26. First-cleavage spindle forming. Germ nuclei have not fused; the 

 chromatin strands, in two groups, have not yet formed definitive 

 chromosomes. Bouin's fluid, iron hematoxylin and Congo red. 

 X 1600. 



Fig. 27. First-cleavage spindle forming. Germ nuclei have already fused 

 into a single vesicle; chromosomes not yet formed. Bouin's 

 fluid, picro-hematoxylin. X 1600. 



Fig. 28. Second-cleavage spindle almost completed, nuclear membrane not 

 yet ruptured. Chromosomes forming. Flemming's fluid, iron 

 hematoxylin. X 1600. 



Fig. 29. Group of germ cells from gonophore; o'go^., oogonia before last 

 division; o'gd'., oogonia in last division; o'cy^., oocyte formed, 

 chromatin in dense mass; o'cy'^., chromatin of oocyte beginning 

 to form a thread, nucleolus present; o'cy^., oocyte after growth 

 has started, chromatin in a spireme. Corrosive-acetic, iron hema- 

 toxylin. X 1600. 



