CRUSTACEA. 121 



who was aiding M. Coste in his experiments, dis- 

 covered that the curious little beings known as 

 Pliijllosoma are nothing more than the larvce or 

 young forms of the crawfish. The egg of the craw- 

 fish, on quitting the mother, becomes a Phyllosoma, 

 which is afterwards changed into a perfect craw- 

 fish. The metamorphosis is as complete as with 

 insects. 



Professor Thomson, of Belfast, discovered for- 

 merly that certain crabs gave birth to curious- 

 looking beings, to which a French naturalist had 

 previously given the name of Zoea, These Zoea, 

 which were looked upon as distinct animals, turn 

 out to be the larvae or young of other well-known 

 Crustacea. Similar facts have recently been made 

 known by Mr. Couch, of Penzance.* But since the 

 publication of Professor Thomson's observations, 

 we have, in the order of Entomosiraca, examples of 

 generation equal to that we mentioned in speaking 

 of the Aphides in a preceding chapter. M. Hasse 

 has also shown that the curious creatures known as 

 Praniza are only larvce of Anceus, so that metamor- 

 phosis is doubtless as -active in Crustaceans as in 

 Insects. 



It is now an established fact, therefore, that 

 the eggs of crawfish bring forth larvae which do not 

 resemble the parent, but were formerly classed as 



* Brit. Ass. Report, 1857. 



