The Structure of the Annelids. 869 



worms, confirmed by Lyonnet, Reaumur, Singes, etc., were 

 timidly questioned by Vandelius, and by Bosc, and more re- 

 cently and positively by Williams, Vogt, and others. We 

 must, therefore, be thankful to those who called attention to 

 early observations, like Baircl, or made fresh experiments, like 

 Quatrefages. 



The restoration of mutilated parts of Annelids is incon- 

 testible. Many of them can reproduce even the anterior 

 region with the head. Amongst recent authors, M. de Quatre- 

 fages has demonstrated this fact over again in Eunice, and 

 Dalyell followed step by step the reproduction of the head 

 and branchiae by the posterior extremity of a Sabella. I have 

 also met several times with marine worms (Eteone, Nepthys, 

 etc.) which have undoubtedly reproduced their anterior region, 

 the restored portions being distinguished by lighter colour 

 and smaller diameter. The aspect of these worms resembles 

 that of the Heteronereids ; so great is the difference in the 

 two regions, one would think they were two portions of dif- 

 ferent worms stuck together. One interesting remark occurs 

 with reference to this subject : If a worm is severed trans- 

 versely, does the posterior part always reproduce exactly the 

 number of segments in the suppressed anterior portion ? It 

 is probable. At least I met with an Eteone which reproduced 

 an anterior portion of nearly fifty segments. The head is un- 

 doubtedly the first to be formed, and then fresh segments are 

 successively produced at the junction of the old part and the 

 new. This, however, requires to be supported by positive 

 observations. 



Geographical Distribution of Annelids. — In this section M. 

 Claparede disputes the accuracy of M. Quatrefages in limiting 

 the locality of species. M. Quatrefages does not admit, for 

 example, that the Mediterranean and the ocean can be inhabited 

 by the same species, and sometimes makes specific distinctions 

 out of the fact of locality only. He also maintains that littoral 

 species cannot live under such changes as the presence or 

 absence of tides. At Naples, however, M. Claparede kept 

 littoral Annelids for months in captivity, and found the best 

 mode of making them prosper was to deprive them of water 

 for some hours each day, in order that the vessel might be 

 oxygenated. 



Classification. — On this subject M. Claparede remarks that 

 we are approaching a natural classification, and that the fami- 

 lies now established are for the most part well founded. He 

 does not propose any new families. 



vol. xn. — no. v. E B 



