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



might be seen in the interior, which appeared still plainer when 

 the little animal was fed with indigo. I then found that the 

 intestinal canal was divided into two parts, the stomach (f) 9 

 in the form of a sack, which extends posteriorly and some- 

 what downwards, and the intestine (g) which is separated 

 from it by a contraction, and then growing still narrower 

 ascends directly upwards to the anus. Almost in the middle 

 of the lower raised surface of the animal was a minute spot (i), 

 more opake, and placed diagonally, which in some individuals 

 exhibited two small black points. From this structure it was 

 easy to guess that the animal was not developed, but it was 

 more difficult to say what it would change to. 



This question was however soon solved. It was evident 

 that the little animals, one after the other, underwent consi- 

 derable changes. The upper elevated side (b) projected more 

 and more, and divided into rings (fig. 2, i). The first of these 

 formed themselves near to the anus (h), and their number 

 increased by degrees, so that the last one added lay next to 

 the disc. Each newly-formed ring consisted of four parts. 

 Two of these semi-rings, the anterior and hinder, were large, 

 and covered externally w r ith muscular layers, and the other 

 two shorter side-pieces united them. Whilst this change 

 went on upon the disc, one quite as surprising took place 

 below it. The above-mentioned spot constantly became 

 more opake and distinct, and between the black points and 

 in front of them were formed by degrees near the eyes (figs. 2, 

 3, 4), pointed filaments, which were the tentacula. The ob- 

 ject of this uninterrupted metamorphosis now became appa- 

 rent ; it was evidently the development of an Annelide. The 

 form now described and represented in fig. 2. very soon changed 

 into that which is seen in fig. 5, w T hilst the number of the rings 

 rapidly increased, and the former round, arched part (b) be- 

 came the curled body of a worm. The disc, with its vibrating 

 cilia, still existed, and the little animals, which had been two 

 days captured, died one after the other. I was upon the 

 point of renouncing the hope of pursuing their development 

 to its end, when at last I found one which had survived 

 longer, and which I have represented in fig. 6 : this had no 

 longer the ring provided with cilia round about the head (as 

 fig. 5.), which was stretched freely forwards, and as a remnant 

 of the ring, appeared on each side an appendage, without any 

 decided form ; the animal soon after died. On this account 

 I cannot decide whether this appendage still remained fixed 

 any time, or soon fell off; I had, however, reason to suppose 

 the former. Several years ago I had already observed and 

 sketched a small Annelide, which was swimming on the sur- 

 face of the sea, resembling the one now described, but more 



