50 The Unity of the Organism 



tween the two is established. On the contrary in the state- 

 ment that the polarity, symmetry and pattern of the egg 

 are determined by the cytoplasm, the determination is im- 

 mediate and observed. Manifestly in a literal sense "de- 

 termined" is properly used in the second connection but not 

 in the first. The cytoplasm is operative on the spot, so to 

 speak, in the second case. It is concerned with an immedi- 

 ate result. The germ-cells on the other hand are not really 

 determiners. They are not concerned with an end result, 

 but are if anything instigators of a long developmental 

 series at the far end of which appear the attributes in 

 question: skin, color and the rest. 



If this case of spinule production stood alone as an 

 instance of specific characters in adult animals traceable 

 to cytoplasmic activity of individual cells, it would be a 

 rather small base on which to erect a general argument in 

 favor of cytoplasm as inheritance material. But it does 

 not stand alone. Indeed, the company to which it belongs 

 will almost certainly be found to be legion when systematic 

 investigation of the subject shall have been made. 



The Spicules of Sponges and Other Invertebrates 



I will cite a few more cases. In several widely separated 

 groups of animals, spicules, usually either calcareous or 

 silicious, are present in some of the tissues. These are often 

 produced by one or a very few cells, and often, too, their 

 shape, size, and probably other attributes differ from 

 species to species even of the same genus. 



The spicular system reaches its greatest development and 

 has been most studied in sponges. "The spicules of 

 sponges," writes Sedgwick, "in the diversity, symmetry, and 

 intricacy of their form, in the perfection and finish of their 

 architecture, constitute some of the most astonishing ob- 

 jects in natural history." 13 Figure 48 gives a hint of the 



