Prof. E. Claparede on the Structure of the Annelida. 347 



sages* in which I mentioned these organs, and cited an analo- 

 gous observation of M. Keferstein; but by a singular mistake 

 he makes us describe convolutions of blood-vessels, whilst we 

 speak very positively of glandular coils. Such a confusion is 

 hardly possible; for the passage relates to Nereids, in which the 

 coils in question are colourless, whilst the vessels are of a fine 

 red colour, M. Kolliker was the first to discover, in Sphcero- 

 dormn peripatus, that each coil of the glomerules contained in 

 the spherical appendages opens outwards by a separate pore. 

 This observation has just been repeated by M. R. Greef in 

 Sphcerodorum Claparediif. 



Muscular System. 



The muscles of the Annelida present extraordinary variations 

 in their histological structure, as I shall have more than one 

 occasion to show in the course of this memoir. Sometimes they 

 are composed of fibres with parallel edges and entirely destitute 

 of nuclei, sometimes, on the contrary, of fibre-cells furnished 

 with large nuclei. 



The existence in the Annelida of fibre-cells of a muscular 

 nature has indeed been entirely denied by M. Schneider |. But 

 although this naturalist may be right in the immense majority 

 of cases, we shall see that this rule is liable to some exceptions 

 (pharynx of certain Nereidea, tentacles of various Terehellea, &c.). 

 Sometimes the muscular fibre separates into two distinct layers 

 (one axial, the other cortical), as M. Leydig was the first to 

 remark §. Nowhere is this structure so distinctly shown as in 

 Nephthijs. Lastly, in some Annelida, as M. de Quatrefages very 

 justly indicates, the muscular system undergoes a remarkable 

 simplification, in the loss of its fibrillar structure. Sometimes 

 we find, in place of the muscles, nothing but a contractile proto- 

 plasm with nuclei dispersed through it. Of this we shall indi- 

 cate some examples hereafter. 



The * Histoire Naturelle des Anneles ' indicates between each 

 segment a sort of tendinous raphe upon which the muscular 

 fasciculi are inserted ||. These raphes have no existence. It is 

 easy to ascertain, from longitudinal sections of Annelida, that 

 the longitudinal fasciculi are continued without any interruption 

 throughout the length of the worm. This has already been 

 seen and described by Ue Blainville, Delle Chiaje, Rathke, 

 Meckel, &c. 



* Beobacht. &c. p. 52. 



t See ' Annals ' for July, vol. xx, p. 4 et seq. 



X "Uebcr die Muskeln iler Wiirmer, &c.," Miillei-'s Archiv, 1864, p. 590. 

 § " Ueber Phreoryctes Meiikeanus," Archiv fiir niikrosk. Anat. Band i. 

 p. 249. 



11 This notion, however, is revived froixi Ciivier, 



