352 Prof. E. Claparéde on the Structure of the Annelida. 
suppose that there is only one vessel. As to the supposed am- 
pullze, these are the projections of the vascular loops. It is only 
necessary to turn the branchie 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 Terebelle and Arenicole, 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 Cirratulea, M. Schmarda in Nephthys, Dr. 
Johnston in the Nerine, 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 side} in the interior 
of the branchia, at the same time emitting numerous vascular 
branches {. But all these observations have remained dead 
letters to the author of the ‘ Histoire Naturelle des Annelés.’ 
- I have stated that all Annelida present the typical structure | 
of the branchize, except the Serpulea. _I must, however, add 
that one family presents a remarkable simplification of this 
organization. This is the family Sprodea. Throughout this 
family the branchize only contain the two principal vessels, the 
artery and the vein ; the lateral loops are wanting. 
The lymphatic branchie will form the subject of a special 
investigation, in the Annelida which present them (Sigalionida, 
Dasybranchi, Glycere). 
* Jstituzioni di Anatomia comparata, 2 ediz. tome ii. p. 76. Naples, 
1836. 
+ This description is very correct, as we shall see hereafter in connexion 
with Diopatra neapolitana (Delle Chiaje). 
{ M. Milne-Edwards, that excellent observer, has likewise recognized 
the duplicity of the branchial vessel; but, in his ‘ Legons sur la Physiol. 
et l’Anat. des Animaux’ (tome iii. p. 217), he has modestly put his own 
observations into the shade, in order to set off those of M. de Quatrefages 
and proclaim the existence of a cecal vessel with ampulliform diverticula. 
The observations of M. de Quatrefages upon the branchiz of the Glycere 
and Polydore, the only ones that he cites, appeared to him decisive. M. 
de Quatrefages has been unfortunate in the selection of his examples: 
the Polydore, with their simple branchial loop, cannot produce the illu- ° 
sion of the ampulliform diverticula; and the Glycere haye no vessels at all!. 
