The Structure of the Annelids. 269 



long* before the differentiation of the nervous system; and 

 when this system is developed, the number of ganglions is not 

 necessarily identical with that of the primitive segments. 

 Amongst Annelids, in particular, the formation of a nervous 

 system sometimes follows pretty closely that of the segments — 

 among the embryos of the Capitelles, for example — but it is 

 usually later. I do not dispute that among many Annelids the 

 birth and distribution of nerves conform to the rule of M. 

 Quatrefages. But we see that in certain cases it is not the 

 buccal segment only, but also some of the following segments, 

 which receive their nerves from the cesophagal connexions. It 



is so among certain Aphroditians, Hesionians, etc I 



employ the name Antenna for all the appendages of the 

 cephalic lobe ; but when two of these appendages spring from 

 the inferior portion of the lobe, and present special anatomical 

 and physiological characters. I, in common with the majority 

 of authors, call them palpi. The modified cirri of the buccal 

 and following segments are called in this memoir tentacular 

 cirri." 



" Without wishing to dilate on the conformation of the feet 

 of the Annelids, I would indicate the relation of the bristles to 

 the tissues environing them. Some authors consider them as 

 enclosed in a pocket which is merely an invagination of the 

 teguments, and others think they are engendered in an internal 

 follicle, and only arrive in a secondary way at the surface. 

 This second opinion is correct. Among the Hesions and 

 others, for instance, the whole bunch of bristles come in a 

 compact form out of a single pedal opening, but in other cases 

 each bristle has its own special aperture. This is especially 

 the case with the flabelliform tufts. The issuing pore of each 

 bristle is not preformed. The bristle makes its own perforation, 

 which is easy when the tissues are soft, but it is not so when 

 the worm is protected by a resisting cuticle, and when the 

 bristle, armed with hooks in different directions, might 

 entangle themselves in the tissues, and produce serious rents. 

 In these cases the extremity of each bristle is surmounted with 

 a small provisional apparatus, terminating in a very keen 

 blade, destined to cleave a free way for the bristle, and to 

 avoid tearing. The form of this cutter varies much with that 

 of the bristle, and especially of the hooks, whose passage must 

 take place without tension of the adjacent parts." 



Teguments and Muscular Apparatus. — " The teguments are 

 composed of two layers — one internal and cellular {Gorium, 

 Bathke, derme, Quatrefages), corresponding to the sub-cuticular 

 or chitinogeuous layer of other Articulata; the other extra- 

 cellular, the cuticle (epiderme, Rathke, Qtrfg.) sometimes very 

 delicate, sometimes composed of a thick layer of chitin. Up 



