On the Young Stages of a few Annelids. 337 



Claparede has fully demonstrated that neither the classifications 

 of Busch, Miiller, nor Schlutze, will satisfy the facts thus far 

 observed, and it seems probable that Claparede's classification 

 must share the same fate ; we should only remember that all 

 these attempts are based upon such few and incomplete ob- 

 servations that we cannot expect them to apply to subsequent 

 discoveries. The features used by Claparede to make his sub- 

 divisions seem somewhat objectionable, as it would be impos- 

 sible, unless the complete development of the larva were 

 known, to ascertain to which of his divisions they belong; and 

 yet these characters are, as far as the development of Anne- 

 lids is now known, the best that have been proposed. The 

 presence of temporary bristles is a good criterion for one divi- 

 sion, and appears to be connected with fundamental differences 

 in the larvae, though the other division, based upon their ab- 

 sence, is liable to the usual objections ot characteristics derived 

 from negative features alone. How much more remains to 

 be done before any such classification of the Annelid larvae 

 can be attempted with the least chance of success, is best shown 

 by examining in any tabular view the number of families of 

 which we know nothing as yet of their embryonic conditions. 

 And though Krohn, Max Miiller, Van Beneden, Wagener, 

 Schneider, Keferstein, Pagenstecher, and others, but more espe- 

 cially Claparede, have lately done so much to advance our 

 knowledge of the development of Annelids since the time of 

 the first papers by Loven, Sars, Milne Edwards, Quatrefages, 

 and Miiller, we can hardly be said to have more than com- 

 menced the investigations of the development of the Anne- 

 lids proper, which in this respect are far behind the intesti- 

 nal worms, and we must wait for further observations before 

 classifications of embryonic Annelids can be of material ad- 

 vantage for systematic studies. 



Among the young Annelids not yet traced to their adult 

 condition, I would figure two forms totally unlike any hitherto 

 described. They both come in the group of Metachaetae of 



