370 THE NATURAL HISTORY REVIEW. 



is a combination of the first and second of these methods, the prolifi- 

 cation of Autolytus cornutus, the development of which we proceed 

 to consider, belongs partly to the first group, and partly to the third. 

 The female Autolytus cornutus is about half an inch in length, of a flesh 

 colour. The alimentary canal appears as a green tube extending from 

 one end of the body to the other ; th| posterior and the anterior 

 rings are of a greenish hue. The cephalic segment has three long 

 tentacles, one, the longest, in the centre, the other two on either side. 

 The ova in their earliest stages of development are found thickly packed 

 between the walls of the alimentary canal and the outer body wall — 

 along the whole length of the annelid. As they increase in size, filling 

 more and more of the perivisceral space, there is developed on the lower 

 side of the body a large receptaculum into which they pass ; when fully 

 swollen with ova, this pouch extends from the 12th to the 25th or 26th 

 ring. In it the ova are hatched and soon afterwards the young embryos 

 — the envelope of the pouch bursting — escape, and swim freely about. 

 It is probable that the females are killed by this bursting of the uterine 

 pouch, as A. Agassiz never succeeded in finding a single female after 

 it had discharged its embryos. The young Autolytus is triangular in 

 shape, and is provided with two large eyes : the alimentary canal 

 follows the outline of the young embryo, and there is no appearance of 

 a mouth. In its next stage, there is an indentation behind the eyes, 

 thus separating the head slightly from the body, the alimentary canal 

 as well as the young embryo assumes a more elongated shape, and the 

 former is divided by two constrictions into three regions. In the 

 next stage, the embryo is divided stiU more plainly by the constric- 

 tions — the three regions of the alimentary canal are better marked, 

 the head with the eyes is more distinct, the triangular shape has 

 completely disappeared, and the mouth can be seen as a small slit on 

 the lower surface, then the middle tentacle is seen ; next the lateral 

 tentacles appear in advance of the eyes, these soon outstrip in growth 

 the middle tentacle, the anterior rings are provided with bunches of 

 stifi" bristles, and the anal ring has on each side one small anal cirrus. 

 The tentacles of the head go on increasing in length — some additional 

 rings are formed, and bristles are found on each ring except the first 

 and last ; when it has reached this stage the embryo does not increase 

 in length until the appendages of the dift'erent rings are so well 

 developed that it can be unmistakeably recognized as a parent stock 

 of Autolytus with a small number of rings. The anal cirri increase 

 in length, slight swellings make their appearance on the sides of the 



