46 The Unity of the Organism 



and S. montereyensis) , or it. may be serrate (figures 44, 45 

 S. yakutatensis, S. plicata). 



Viewing this case in the light of considerations put for- 

 ward on the preceding pages, the pertinent queries about 

 the heredity of the shields almost ask themselves : What is 



FIGURE 46. SPINULE CELL OF STTELA GREELEYI (AFTEE HUNTSMAN). 



the "inheritance material" that causes the shield to be short 

 and truncate in S. yakutatensis and long-pointed in S. 

 greeleyi; or that explains the serrated edge in S. yakuta- 

 tensis and S. plicata as contrasted with the smooth edge in 

 S. montereyensis and S. greeleyi? Is the "seat" of that ma- 

 terial in the cytoplasm or the nucleus of the shield-produc- 

 ing cell? Unfortunately we have no direct observational 

 information about the genesis of the spinules. But the 



