The Structure of the Annelids. 271 



their relation to the external pores is very remarkable. The 

 formation of these organs is still entirely problematical. I have 

 sometimes compared them to the cells full of needles of the 

 Turbellarians, and to the stinging organs of the Acalephs, etc., 

 but this is mere hypothesis." 



" Tubular glands full of spherical granulations have been 

 pointed out by us in divers Annelids. Sometimes they reach 

 considerable dimensions, particularly among the Lycoridians, 

 and in this case the glomration formed by the junction of 

 glandular tubes was known to old authors and considered to 

 be a sac. M. Quatrefages knew of one of the passages in 

 which I had spoken of these organs, and cited an analogous 

 observation of M. Keferstein, but by a singular blunder, he 

 makes us describe circumvolutions of blood vessels when we 

 spoke very positively of glandular branches fboyaux). . . . 



Muscular system. — The muscles of Annelids exhibit extra- 

 ordinary varieties in their histological character. Sometimes 

 they are composed of parallel fibres quite destitute of a nucleus, 

 and at others of fibre-cells furnished with large nuclei. The 

 existence of these fibre- cells of a muscular character in Annelids 

 has been, it is true, denied by M. Schneider ; but cc although 

 this savant is right in the majority of cases, we shall see that 

 the rule suffers certain exceptions in the pharynx of some 

 Nereids, tentacles of many Terebellians, etc. Sometimes the 

 muscular fibre separates into two distinct layers, one axial, the 

 other cortical, as Leydig first observed." 



" The ' Historie Naturelle des Anneles ' describes between 

 each segment a sort of tendinous raphis, in which the muscular 

 fascise insert themselves. These raphids have no existence. 

 It is easy in longitudinal sections of Annelids to see that the 

 longitudinal fascia? are continued without interruption the 

 whole length of the worm. This is what Blainville, Delia 

 Chiaje, Bathke, Meckel, etc., observed. Muscular plates more 

 or less complete, sometimes divide the previsceral cavity into 

 several chambers. Thus the Ophelians, Polycirridians, and 

 many Terebellians, the Aphroditians, and the majority of the 

 wandering Annelids have three divisions in the perivisceral 

 cavity, the Glycercians two, etc." 



Digestive Organs. — M. Quatrefages has endeavoured to 

 establish a new nomenclature for different parts of the alimen- 

 tary tube, the necessity for which may be disputed. Why, 

 for example, in the Syllidians give the name dental region of 

 the proboscis to the organ with glandular walls, which does not 

 form part of the proboscis, and contains no teeth.* The 



* la a note, M. Claparede says that M. Quatrefages has enumerated certain 

 Syllidians as having teeth in this regioa, but has mistaken the specie?, "which belong 

 to quite different families. 



