THE EVIDENCE FROM DEVELOPMENT. 



219 



however, being singular in respect of the obliteration of the inter- 

 mediate stages. The king-crabs have presumably originated m the 

 common Nauplius-form, and have passed through the Tnlobite-form, 

 now extinct, to their present position at the extremity of an isolated 

 branch of the crustacean tree ; although, indeed, some naturalists 

 hold that the king-crabs are more nearly allied to the spiders and 

 scorpions, than to the Crustaceans. The barnacles, fish-lice, and 

 water-fleas, obviously nearly allied, spring from a distinct Nauplms- 

 stem, but diverge through different ways and paths of life the former 

 to exist mostly as degraded parasites, and the latter to develop into 



Penaeus (fig. 132). 



Lobster (fig. 129). 



Crayfish. 



Nauplius (figs. 119, 121, 122, 123, 133). 



active free-swimming forms. Thus becomes clear to us the meaning 

 of those singular changes in animal forms which puzzled the older 

 naturalists. To question the meaning which evolution attaches to 

 these changes, is to leave them without explanation or meaning. Our 

 knowledge of the full evolution of the Crustacea or any other animal 

 group, as already remarked, may be, and often is, far from perfect. 

 We are, it is true, still in the " grey mists " of many biological 

 subjects, and the pedigree of animals, amongst others, is still 

 enveloped in much obscurity ; but, at the same time, we can detect 

 breaking through the mist, gleams of knowledge bright forerunners of 

 that flood of light w'hich the research of after-years will assuredly bring. 



