of a few Annelids, 209 



done by Claparede in his classification of Annelid larvae. From 

 what is shown hereafter (and we have, as far as I know, no 

 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 Nereidse or Eunicese, 

 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 Annelids, 

 to find in somewhat more advanced stages that these tenta- 

 cles 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 

 Turbellarise, and probably to some Nemertean genus like Nareda 

 of Girard. 



We find, in stages subsequent to those figured by Loven 

 (figs. 14 and 17), that the antennse 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 building their case. 

 Loven observes that the absence of feet and bristles prevented 

 him from ascertaining the genus to which his young Annelid 

 belonged ; while it is this very absence of feet and bristles, as 

 well as the distinct separation of the digestive cavity into oeso- 

 phagus, stomach, and intestine, plainly described by him in his 

 young worm, which should have guided him, as well as subse- 

 quent writers on this subject, in referring the larva to its proper 

 place. Had it not been for the deceptive appearance caused 

 by the temporary presence of antennse and their resemblance 

 to Polynoe larva), this would undoubtedly have been done long 

 ago, especially when taking into consideration the differentia- 

 tion of the digestive cavity, so prominent in Loven's larvae: 

 this separation takes place in other Annelid larvae long after 

 the family (and sometimes even the generic) characters have 

 been fully developed. The early growth of bristles, and the re- 

 semblance of the young larvae of Polynoe to the adult at so 

 young a stage, should at once have directed attention to such 

 an anomalous type as that of Loven's, having no feet or bristles 

 long after the young worm had lost its embryonic character 

 as well as all trace of the row of vibratile cilia round the head. 

 The passage of Loven's figures from the condition with a disk 



