On the JToung Stages of a few Annelids. 317 



The oral and anal vibratile cilia disappear rapidly (Figs. 12, 

 13), the head becomes more rounded, the antennae having 

 attained their maximum size (Figs. 12, 13) grow less and less 

 prominent, and rapidly vanish, so that the head of the young 

 worm has now the shape of Fig. 14, which was its condition 

 four months after the stage represented in Fig. 11. The articu- 

 lations have become obliterated, no trace can be found of the 

 pigment spots, which have gradually grown smaller and less 

 numerous, and the young worm in its motions and attitudes 

 reminds us strongly of Nemertes and the like Annulata. About 

 a month later the head is even less prominent, and is separated 

 from the body by the characteristic neck of the Nemerteans, 

 the tentacles having altogether gone, the only trace of them 

 being very slight swellings on each side of the head. The 

 young worm loses at the same time its cylindrical shape, and in 

 Fig. 14; has already become greatly flattened. This is quite 

 well shown in Fig. 16, a profile view of Fig. 15. The young 

 Nemertean is now nearly half an inch long, and is usually 

 found slightly coiled on the bottom of the jar in which it is 

 kept ; on being disturbed their motions are somewhat like those 

 of the Nemerteans. The posterior extremity is much smaller 

 than the anterior, the width of the worm increasing towards the 

 head. As it grows older this difference is lost, the head be- 

 comes still less prominent, and finally in Fig. 17, when the 

 young worm is five months older than Fig. 11, the w T idth of the 

 head is less than that of the body, and the eyes have moved 

 nearer the neck. 



There is but little doubt from the foregoing observations, 

 that Loven's larva becomes eventually a Nemertean, closely 

 allied to Polia ; my oldest larvae were, however, far from being 

 adults, and their generic affinities cannot be more closely inti- 

 mated at present. There is little exceptional in the develop- 

 ment of the larva from that of the other Annelids, as has been 

 maintained, and like other Annelids it early assumes the 

 features of the adult, and new rings are developed next to the 



