342 Prof. E. Claparede on the Structure of the Annelida. 



"cephalic lobe'^ {prcpstomium, 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 antennce to all the appendages which 

 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. AVhat 

 a difference there is, in particular, between the palpi [antennes 

 later ales, Aud. & Edw., Quatref.) and the frontal antennre 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 (Kinbei'g and all recent authors) and the true antennae 

 in the Aphroditea ! So true i .his, that M. de Quatrefages has 

 not been able to remain faitnful to his principle in all cases. 

 Thus, in the Spllidea, he retains the name of frontal lobes for 

 organs evidently homologou.s with the palpi of the Lycoridea, 

 and which ought, consequently, in his nomenclature to bear the 

 name of anteimce. 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 antennae f. 



* De Bopyro et Nereide, commentationes anatomico-physiologicse (Iuje. 

 Riga et Dorpat, 183/, 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 antenuje. 



