310 On the Young Stages of a few Annelids. 



considered by Milne Edwards as simply due to the distension 

 of that portion of the young Annelid, similar to what he had 

 often observed in some of the younger stages of Terebella 

 while in motion. Larvae with similar disks have since been 

 observed by Sars, Busch, Miiller, and Claparede, which are 

 known to be the young of Polynoe. It was, therefore, to judge 

 from the general resemblance of these larva?, most natural to 

 associate Loven's larva with those of Polynoe, as has been 

 done by Claparede in his classification of Annelid Larvae. 

 From what is shown hereafter — and we have, as far as I know, 

 ho exceptions to this in the embryology of Annelids — there are 

 points of difference showing at once that the association is not 

 a natural one. The oldest stage figured by Loven has as yet 

 no trace of any feet or bristles, and the only feature by which 

 it might possibly be associated with the Nereidae or Euniceae, 

 as has been done by Loven, is the presence of two short an- 

 tennae at the anterior extremity. We should expect, from 

 what has been shown thus far by all writers on young Anne- 

 lids, to find in somewhat more advanced stages, that these ten- 

 tacles have considerably increased in length ; but such is not 

 the case in the specimens of a closely allied species which I 

 have had the opportunity to observe, and to keep alive long 

 enough to leave but little doubt that Loven's larva does not 

 belong to the Rapacious or Tubicolar Annelids, but to the 

 Turbell arise, and probably to some ISTemertean genus like 

 ISTareda of Girard. 



We find in stages subsequent to those figured by Loven, 

 Figs. 14, 17, that the antennae gradually disappear by a sort of 

 retrograde metamorphosis, similar to that of Terebella, ob- 

 served by Milne Edwards and Claparede, where the young, 

 resembling far more the normal type of rapacious Annelids 

 than the adult, lose their few rudimentary organs of sense and 

 locomotion soon after they have commenced to build their 

 case. Loveii observes that the absence of feet and bristles 

 prevented him from ascertaining the genus to which his young 



