314 MENSCH. [Vol. XVI. 



position of the chain in the same species as being accidental 

 rather than due to any particular cause. The appearance of 

 several specimens observed, and the difference in size and 

 apparent age of the parent stock in individuals in which there 

 is a great difference in the position of the stolon, together with 

 the fact that in Autolytus cornutus and in Procerea the position 

 of the stolon is so constant, has caused me to regard the range 

 in the position of the chain as being due to more than mere 

 accident. In this species there is, without a doubt, a distinct 

 difference between the age of the parent stock with 56 or 59 

 segments and that of 19 or 20 segments. This is indicated, 

 both by the size and more mature appearance of the parent 

 stock, in which the largest number of segments occur, and also 

 by the distribution of the red color-spots, which equally indicate 

 the difference in age between the young individuals without 

 stolons, or those in which stolonization is just appearing, and 

 the chain-bearing individuals. Furthermore, specimens are- oc- 

 casionally found in which the line of demarcation between the 

 posterior segment of the parent stock and the anterior segment 

 of the chain is not sharply defined by the great difference in 

 the size of the segments as it is in the specimens usually found. 

 One specimen of this kind which I have observed showed an 

 anterior segment of the chain that was very much larger than 

 the second segment of the chain, and had attained a size nearer 

 to that of the last segment of the parent stock. No parapodia 

 were present in this segment, and the only indication of a con- 

 dition differing from that of the ordinary was the increased size 

 of the segment. In another specimen, however, I found a simi- 

 larly located segment bearing parapodia, and presenting all the 

 characteristics of a segment of the parent stock, but the small 

 size of the parapodia, and the less mature appearance of the 

 segment, gave evidence of its having more recently been added 

 to the parent stock. Such specimens would accordingly indi- 

 cate that the embryonic region not alone furnishes segments 

 for the formation of stolons, but also contributes segments for 

 the elongation of the parent stock. 



Evidence that additions to the number of segments of the 

 parent stock may occur abnormally can occasionally be obtained 



