TR1LO BITES AND OTHER FOSSIL CRUSTACEA. 183 



Crustacea, we must allow that the Trilobites were 

 affected in the same manner. The number of larval 

 stages they passed through depends upon the position 

 they attained as regards organization. This was much 

 higher than Haeckel imagines, and therefore the 

 stages may have been numerous. It is to be expected 

 that individuals would die and be buried in the muddy 

 ooze in each of these intermediate states. Thus found, 

 what more natural than to regard them as different 

 species, and even different genera ? Only a fuller 

 knowledge of crustacean embryology will clear away 

 a good deal of the useless nomenclature which has 

 gathered about these interesting creatures, and it is 

 hardly to be expected that we shall ever know their 

 accurate life-history. Barrande, who had such splen- 

 did opportunities for studying the Trilobites, and who 

 made equally good use of them, satisfied himself, in 

 the case of no fewer than twenty different species of 

 Trilobites, that they passed through larval stages, each 

 unlike the other. In some instances he traced them 

 from when they had only just escaped from the egg 

 to the fully developed and mature state. In the first 

 instance they had no joints to the body, and there- 

 fore strongly resembled one of the carapaces of the 

 "water-fleas;" in the last they possessed ring-covered 

 bodies, movable tails, and compound eyes. This 

 proves that, although in their young states Trilobites 

 resembled the Ostracoda, in their adult life they had 

 oroceeded much further. Parallel with the instance 



