266 THE APODIDJE TART n 



from a larval stage of Apus, dating back to the time 

 when the Apodidae could no longer develop fully in 

 the open sea, and only those larvae which were acci- 

 dentally shut off and isolated in lagoons were able to 

 grow into adult animals. 



CIRRIPEDIA. 



These animals are now generally supposed to be 

 related to the Copepoda. What we have said of 

 the latter applies in great part to them also. We 

 can deduce them from no original adult Crustacean 

 form derivable from our bent Annelid. We are there- 

 fore driven to deduce them, as we have done the 

 Copepoda, from some larval form. We think it pos- 

 sible that the Cirripedia may have been one of the 

 extraordinary lines of development adopted by the 

 original Copepod, i.e. larval Apus, which sought 

 safety in a stationary life. As larvae of Apus, it was 

 always possible for them to develop the shell-fold or 

 mantle if necessary, the later calcification of which, 

 perhaps as protection against the browsing Trilobites, 

 led to the beautiful shell arrangements characteristic 

 of the group. 



We now come to groups the origin of which can be 

 established with less appeal to the imagination than 

 was necessary in the former groups. The manner in 

 which the other Phyllopoda have been derived from 

 the Apodidae will afford some capable zoologist a 

 field for research which cannot fail to be rich in 



