342 Prof. E. Claparéde on the Structure of the Annelida. 
“cephalic lobe” ( prestomium, Huxley) to everything situated 
in advance of it. I adopt this view, which has the advantage of 
not attempting to solve the question, still undecided in many 
cases (Glycera, Nemodrilus, &c.), of the number of segments 
composing the cephalic lobe. Moreover the buccal segment is 
often so similar to those which follow it that it is hardly possible 
to refer it to a different region. M. de Quatrefages, taking up 
an opinion already maintained by Rathke*, regards the cephalic 
lobe and buccal segment as together forming the head; but he 
does not himself adhere too rigidly to this opinion, since in his 
descriptions he most frequently gives the name of head to the 
cephalic lobe alone. 
M. de Quatrefages has endeavoured to introduce a simplifica- 
tion in the nomenclature of the appendages of the cephalic re- 
gion, by giving the name of antenne to all the appendages whieh 
spring from the cephalic lobe, that of tentacles to all those of 
the buccal segment, and that of tentacular cirri to those of the 
first feet, when they display characters which distinguish them 
in a marked manner from their homologues belonging to the 
feet placed further back. This nomenclature, which seems well 
chosen at the first glance, nevertheless presents many incon- 
veniences, and is often specifically inapplicable. In the first 
place, the appendages of the cephalic lobe sometimes differ en- 
tirely among themselves both as regards function and structure, 
which has led most authors to give them different names. What 
a difference there is, in particular, between the palpi (antennes 
latérales, Aud. & Edw., Quatref.) and the frontal antenne of the 
Lycoridea |—the former fleshy, multiarticulate, partially retrac- 
tile, and occupied by the expansion of the largest nerve of the 
body; the latter filiform, simple, not retractile, and scantily 
provided with nerves. What a distance there is likewise between 
the palpi (Kinberg and all recent authors) and the true antenne 
in the Aphroditea! So true is this, that M. de Quatrefages has 
not been able to remain faithful to his principle in all cases. 
Thus, in the Syllidea, he retains the name of frental lobes for 
organs evidently homologous with the palpi of the Lycoridea, 
and which ought, consequently, in his nomenclature to bear the 
name of antenne. This homology was demonstrated by Rathke ; 
and no one, so far as I know, has yet contested it. It is true 
that M. de Quatrefages is not always consistent in his incon- 
sistency ; for when in certain Syllidea the palpi become elon- 
gated, he restores to them the name of antenne +. 
* De Bopyro et Nereide, commentationes anatomico-physiologice duz. 
Riga et Dorpat, 1837, p. 26. 
T He restores it to them even with usury; for in the Polybostrichi he 
regards the two palpi bifurcated at the extremity as four antenne. 
