NOMENCLATURE OF THE CCELOM 



15. A nephridium may, as may a uroduct or gonoduct, acquire 

 a secondary element by ingrowth of ectoderm at the nephridiopore, 

 its original external opening. This secondary portion must be 

 termed " nephridiod.eum " (Goodrich), the Avord being formed in 

 the same way as stomodoeum and coelomodaeum. 



16. Nephridia may become "grafted" in various degrees upon 

 uroducts and gonaducts in some animals {e.g. the Polychoetous 

 Annelids), giving rise to organs of complex origin which cannot 

 be termed either " nephridia " or " cwlomoducts," since they have a 

 part of each category in their composition. The composite organ 

 thus formed may be termed a " nephromixium " or " nephromix," 

 in reference to its hybrid composition. 



The object of this introductory chapter is now completed. 

 That object has been the vindication of the ccelom as a morpho- 

 logical factor of primary importance in the animal series, and 

 the maintenance of the conclusion that the ccelom by its presence 

 justifies the separation of a higher grade of Enterozoa, the 

 Ccelomoccela, from a lower grade the Enterocoela, in which it is 

 not differentiated as a separate cavity. 



