M. R. Leuckart on the Young States of some Annelides. 367 



which are subsequently convei-ted into the middle body, and 

 which, as is well known, present by tar the largest appendages. 



The mature Chcetopterus lives in a free tube formed by itself. 

 In this respect it is not without interest that we learn from 

 Busch, that the larvae observed not unfrequently exuded a 

 slimy mass in the last days of their existence, with which they 

 attached themselves to the side of the vessel in which they 

 were kept. 



I regret that during my residence in the Mediterranean I had 

 no opportunity of becoming acquainted, by my own obser- 

 vations, with these interesting larvaj, wliich appear to possess 

 rather a wide distribution. In this case it is probable that many 

 other points of resemblance with the structure of Chcetopterus 

 would have been discovered. But in Nice the larvae of Anne- 

 lides are generally rarities, at least it was so while I was there. 

 Except the spinose forms above described, only a few were dis- 

 covered, and these mostly at a time when my attention was taken 

 up with other investigations. Amongst these few there is how- 

 ever one upon which I may add a few words, although, properly 

 speaking, the name of larva is no longer applicable to it, as it 

 scarcely exhibits any traces of its provisional organs. It is a 

 young Alciope {A. Raynaudii) , which I took up one day in the 

 Bay of Villa Franca with a number of Firoloides, amongst which 

 it was swimming about*. 



The beautiful, transparent little animal (PI. VII. fig. 6) mea- 

 sured 4| lines, and its body consisted of three distinctly sepa- 

 rated regions, — the head with the neck, the true body, and a 

 tail, — although the mature animal, as is well known, exhibits no 

 trace of any such divisionf. The middle I'egion was by far the 

 largest of these divisions ; it measured about three lines in length 

 and nearly a fourth of this in breadth ; it was broadest in the 

 middle and gradually diminished a little towards the extremities, 

 especially in front. In this middle region eight segments were 

 distinctly to be recognized ; they resembled those of the mature 

 animal in every respect, so that I need not describe them parti- 

 cularly. But I may observe, that the bristles of the first pair of 

 pedal tubercles were very nmch shorter and less numerous than 

 those of the others, and especially the hinder ones, which were 

 the most developed in every respect. The neck was considerably 

 narrower than the foremost segment to which it was attached, 

 and probably measured scarcely a third of the greatest breadth 

 of the middle region. It was as long as broad, and exhibited 

 three segments, or rather three pairs of segmental appendages, 



* I also met with Alciope Candida several times iu the Bay of Villa 

 Franca, 

 t See Krobn, Wiegmaun's Archiv, 1845, p. 171. 



18* 



