268 The Structure of the Annelids. 



they exhibit in a marked manner characters which distinguish 

 them from their homologues belonging to the hinder feet." 



" This nomenclature, which at first appears a happy one, has 

 many inconveniences, and is frequently inapplicable to par- 

 ticular species. In the first place, the appendages of the 

 cephalic lobe are sometimes quite different from each other in 

 formation, as well as in structure, on which account most 

 authors have given them different names. What a difference, 

 for example, there is between the palpi (lateral antennae, 

 And. and. Ed. Qtfg.) and the frontal antennee of the 

 Lycoridians. The first are fleshy, many-jointed, partially 

 retractile, filled by the prolongation of the largest nerve in the 

 body ; the second, are filiform, simple, non-retractile, poor in 

 nerves. An equal distance separates the palpi (Kimberg, and 

 all recent authors) and the true antennee of the Aphroditians. 

 ... A second inconvenience of M. Quatrefages' s nomenclature 

 is its inapplicability in all the cases in which the anterior 

 segments are very condensed, and in which it is not possible to 

 determine to which segment a pair of appendages belong. . . . 

 The learned Academician, enamoured of his theory, suppresses 

 by a stroke of his pen the buccal segment of the major part of 

 the Sigalionides — at least, he ascribes to them only i: an 

 indistinct buccal ring, deprived of appendages." Nothing is, 

 however, more distinct than the buccal segment of these 

 worms, only it carries a pair of feet with their bristles, and 

 cannot be a buccal segment according to the theory of 

 M. Quatrefages. Unfortunately, the author does not know 

 that all the Polynoes have bristles on the segment which he 

 regards as buccal, and that it would be necessary to imagine 

 for them a distinct buccal segment without appendages." 



" M. Quatrefages, however, gives a rule difficult of applica- 

 tion, but still a rule for the determination of segments and 

 their appendages. The cephalic lobe and the antennas, he 

 says, receive their nerves from the cerebral ganglion ; the buccal 

 segment and its tentacles, from the oesophageal connections ; , 

 the tentacular cirri, from the ventral ganglionic chain. This 

 proposition cannot be maintained in the face of modern embry- 

 ology. Schaum had already asserted that, throughout the 

 articulata, each segment is characterized by the possession of 

 a ganglion, and from this principle ho denies that the head of 

 the Anthropoda is formed of many united segments. This 

 doctrine was immediately refuted. In fact, the nervous syslvm 

 differentiates itself relatively very late among the Articulata. 

 On the contrary, the appearance of segments — protozonites, as 

 they are called — is, in many cases, the result of one of the first 

 modifications of the blastoderm. These primitive segments 

 unite in groups, and frequently solder themselves together 



