358 PROFESSOR FE, RAY LANKESTER. 
and evanescent, not in the sense of structures which retain a 
primeval simplicity of form. In the course of the ancestral 
development of some other Phyllopoda (not in all), the 
corresponding appendages have entirely disappeared without 
leaving a trace behind them. It is well to bear in mind 
that were the maxillipedes of Apus a little further advanced 
in degeneration, so as to be devoid of the bract, and consist, 
like the “chilaria”! (metastoma) of Limulus, of simple 
setose chitinous plates, we should have no justification for 
calling them “‘ appendages ” at all, and they might very well, 
since no separate ganglion exists for them in the nerve- 
chain, although they receive each a nerve from the ventral 
nerve-cords, be regarded as median processes simulating 
rudimentary appendages. Such a view is very generally 
adopted with regard to processes termed “ paragnathi” and 
“ metastoma,” and with regard to the “ chilaria” of Limulus 
which last, like the maxillipedes of Apus, receive each a 
special nerve from the latero-ventral cords (woodcut, fig. 3, 
chi). 
1 This useful term is introduced by Prof. Owen in his account of Limu- 
lus, ‘Trans. Linnean Soc.,’ 1873. 
