A CHAPTER IN DARWINISM 



29 



Lernseocera again, which in the adult condition is 

 found attached to the gills of fishes, has lost the well- 

 developed legs of its Nauplius childhood and become 

 an elongated worm -like creature (Fig. 8), fitted only 

 to suck in nourishment and carry eggs. 



J-ARVA BALANUS. 



LARVA CHTHAMALUS 



Fig. 9. — Adult Barnacle or 

 Lepas (one of the Cirrlii- 

 pedes). Natural size. 



Fig. 10, — Development of Cirrhipedes (Bar- 

 nacle and Sea- acorn). After Huxley. 



Amongst these Nauplii — all belonging to the great 

 group Crustacea, which includes crabs and shrimps — 

 is one which gives rise to an animal decidedly de- 

 generate, but not precisely parasitic in its habits. 

 This Nauplius is the young of the ship's Barnacle, 

 a curious stalked body, enclosed in a shell of many 

 pieces (Fig. 9). The egg of the Barnacle gives rise 

 to an actively swimming Nauplius, the history of 

 which is very astonishing. After swimming about 

 for a time the Barnacle's Nauplius fixes its head 



