M. S. Loven on the Metamorphosis of an Annelide. 45 



developed, and apparently belonging to another species. It 

 is almost the same which Dr. Johnston has described and re- 

 presented in the e Annals of Natural History/ iii. p. 293. 

 pi. vi. fig. 2, and which he supposed might be the young of 

 Linna^us's Nereis pelagica. Both of these animals seen by 

 him and by me bear upon each side of the head a kind of 

 winged appendage richly provided on the under side with vi- 

 brating cilia; perhaps the tentacula are formed from these. 

 This question remains unanswered, and also the formation of 

 the feet. 



Had I been able to pursue the development for a longer 

 time, it would have become much less difficult to determine 

 the species exactly ; that cannot now be done, and an exact 

 determination of the genus will be difficult to make. In the 

 first place, however, it is clear, from the nature of the head, 

 its eyes, and tentacula, that it is an animal of the class of the 

 free Annelida, Lamarck's Antennati, and amongst these the 

 form of the body appears to point to the family of the Nereida 

 or Eunices. From the form of the head and the number of 

 the eyes we might suppose it to be a Phyllodoce, and species 

 of this genus are not rare upon our western coast [Sweden] ; 

 but without knowing the form of the foot, it is impossible to 

 decide anything about it. 



Short and imperfect as this observation must appear, it 

 proves that at least certain Annelides undergo a kind of me- 

 tamorphosis, which is no less remarkable than that of insects, 

 and some Crustacea. Besides, it shows that the growth in 

 the Annelides takes place in such a way that the new rings 

 are added in front of, and not behind, the older ones, and that 

 the last hindermost ring is the oldest ; or, that the increase 

 takes place furthest from the head, a law which has also been 

 remarked with respect to the Entozoa. It appears also, that 

 every ring originally consists of an upper and an under half- 

 ring, a tergum and sternum, which are united by two side- 

 pieces, from which proceed the feet at a later period. 

 DESCRIPTION OF THE PLATE. 

 Plate I. B. 

 Fig. 1. Represents a young one, as it first appeared. 

 Fig. 2. The same, which has increased in size, and in which seven rings 



have been developed. 

 Fig. 3. The same, from the under side, in order to show the head with eyes 



and tentacula. 

 Fig. 4. The same, in profile from behind. 



Fig. 5. The animal with a greater number of rings, and worm-shaped body. 

 Fig. 6. An individual after transformation of the ring. 



In these figures, a represents the ring or disc; b, the upper or abdominal 

 part ; c, the under or head part ; d, the head ; e, the mouth ; / the stomach ; 

 g, the intestine ; h, the anus ; i, the ventral rings. 



