A CHAPTER IN DARWINISM 



21 



which issues from the egg of this shrimp is known as 

 the " Nauplius form." Many animals very different 

 in appearance from this shrimp make their first appear- 

 ance in the world as Nauplii ; and it appears prob- 

 able that the Nauplius phase is the recapitulative re- 

 presentation of an ancestor common to all this set of 



FIG. 5. Larva of the Shrimp 

 Peneus. 



FIG. 6. More advanced larva 

 of the Shrimp Peneus. 



animals, an ancestor which was not exactly like the 

 Nauplius, but not very different from it. 



The Nauplius of our shrimp gradually elongates. 

 At first it has but three pair of limbs, but it soon 

 acquires additional pairs, and a jointed body, and thus 

 by gradually adding to its complexity of structure as 

 seen in Figs. 5 and 6, it approximates more and more 

 to the adult form from the egg of which it originated. 



And now we are approaching the main point to 



