SECTION XI 

 DEVELOPMENT 



THE NAUPLIUS 



OUT of the egg of Apus is hatched the well-known 

 Crustacean larva the Nauplius, which, with certain 

 characteristic differences for each group, occurs in all 

 essential points the same throughout the whole class. 

 The general likeness of the adult Apus to the 

 Nauplius has, as already mentioned, been pointed 

 out by earlier observers. This likeness, from our 

 point of view, is very easily explained ; Apus being 

 the primitive Crustacean, or at least one of the 

 primitive Crustaceans, the Nauplius is simply the 

 young Apus, the adult developing gradually out of 

 the larva without any metamorphosis worth men- 

 tioning (see Figs. 34, 39, and 41). Thus the 

 Nauplius larva of other Crustaceans is simply the 

 Apus-stage in their development. \Yc repeat this, 

 not as a conclusion only, but in order to use it as 

 an argument in support of the theory set forth in 

 this book. 



