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



justice to the beautiful investigations of M. Milne-Edwards. It 

 is to be regretted that he has not shown the same favour to 

 Rud, Wagner and Rathke. The distinction which he establishes 

 between the arterial and venous currents appears to me to be 

 very just in its principal features. The same view has been 

 entertained by some authors; witness the name of nervarteria 

 given by Delle Chiaje to the ventral vessel — that is to say, the 

 aorta in the sense of ]\I. de Quatrefages. 



The existence of blood-corpuscles in the vessels of certain 

 Annelida is now-a-days indubitable. M. de Quatrefages, in his 

 ' Histoire Naturelle des Anneles/ admits three examples of this 

 — the Ghjcera, Phoronis, and the Sijllidea. The latter alone is 

 of any value. Thus in the GlycercB the red corpuscles belong 

 to the liquid of the perivisceral cavity ; and as to Phoronis, that 

 genus can hardly retain its place among the Annelida. But, 

 without speaking of an old observation of llud. Wagner with 

 regard to a Terebella, which has, moreover, been confirmed by 

 M. Kolliker, other examples may be cited. In the present 

 memoir true blood-corpuscles will be found described in the 

 Opheliea, the Cirratulea, and the StaurocephaliB. 



Respiratory Apparatus. 



M. de Quatrefages has made science actually go back as re- 

 gards the structure of the organs of respiration. This is the 

 weakest part of his book — weak in the introduction, weak in the 

 general remarks on each family. The branchise, in the opinion 

 of the honourable Academician, have a proper structure, which 

 enables them to be always distinguished. "These organs,'^ he 

 says, " are characterized by a single canal, at and from which 

 afferent and efferent vessels arrive and depart. This canal, the 

 proper walls of which are sometimes visible and sometimes in- 

 distinct, is surrounded by a diaphanous substance which seems 

 to be produced by the thickening of the dermis. In this sub- 

 stance are hollowed out ampulliform lacunse more or less deve- 

 loped, and always destitute of proper walls. The whole is 

 surrounded by an extremely fine epidermis, which presents no 

 appreciable structure. Finally, this epidermis is beset with 



vibratile cilia At the end of a variable tune the branchia 



contracts, although no muscular fibres can be discovered in it. 

 The ampullge empty themselves, so as sometimes to disappear 

 entirely. The blood flows through the central canal of the 

 branchia, and, on arriving at the base of the organ, passes into 

 the efferent vessel. In this movement of return it necessarily 

 meets the venous blood, and cannot but become mixed with a 

 certain quantity of blood which has not undergone the action of 

 the air." 



