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



suppose that there is only one vessel. As to the supposed am- 

 pullae, these are the projections of the vascular loops. It is only 

 necessary to turn the branchiae a little, in order to dissipate the 

 first illusion. M, de Quatrefages has allowed himself to be de- 

 ceived by the first examination, as Pallas did long since. 



But this error is not permissible at the present day. It is 

 already thirty years since M. Grube settled it. It is thirty 

 years since, in his anatomy of Pleione carunculata, he in- 

 dicated the occurrence, in the Terebella and Arenicola, of this 

 deceptive appearance, which led Pallas into an error which 

 M. de Quatrefages has now reproduced. He showed that a less 

 superficial examination led to the recognition of the artery, the 

 vein, and the loops which unite them. No microscopist warned 

 of the danger will go and throw himself upon it. Many modern 

 observers have described and figured the duplicity of the axial 

 vessel of the branchia, — amongst these M. Grube and M. 

 Schmarda in the Cirratidea, M. Schmarda in Nephthys, Dr. 

 Johnston in the Nerina, M. Keferstein in the Spiodea, and 

 myself in the Spiodea and Eunicea. At a still earlier period, 

 Delle Chiaje'^ described in detail in Eunice and Diopatra the 

 artery and the vein passing spirally side by sidef in the interior 

 of the branchia, at the same time emitting numerous vascular 

 branches J. But all these observations have remained dead 

 letters to the author of the ' Histoire Naturelle des Anneles.' 



I have stated that all Annelida present the typical structure 

 of the branchife, except the Serpulea. I must, however, add 

 that one family presents a remarkable simplification of this 

 organization. This is the family Spiodea. Throughout this 

 family the branchise only contain the two principal vessels, the 

 artery and the vein ; the lateral loops are wanting. 



The lymphatic branchiae will form the subject of a special 

 investigation, in the Annelida which present them [Sigalionida, 

 Dasybranchi, Glycerce). 



* Istituzioni di Anatomia comparata, 2» ediz. tome ii. p. 7G. Naiiles, 

 1836. 



f This description is very correct, as we shall see hereafter in connexion 

 with Diopatra neapolitana (Delle Chiaje). 



X M. Milne-Edwards, that excellent observer, has Hkewise recof^nized 

 the duplicity of the branchial vessel ; but, in his ' Lecons sur la Pliysiol. 

 et I'Anat. des Animaux' (tome iii. p. 217), he has modestly put his own 

 obsei'vations into the shade, in order to set off those of M. de Qnatrefafes 

 and proclaim the existence of a ca;cal vessel with ampulliform diverticula. 

 The observations of M. de Quatrefages upon the branchia) of the Glycerce 

 and Polydorcs, the only ones that he cites, appeared to him decisive. M. 

 de Quatrefages has been nnfortunate in the selection of his examples : 

 the Polydorce, with their simple branchial loop, cannot produce the illu- 

 sion of the ampulliform diverticula; and the Glycerce have no vessels at all! 



