No. 2.] STOLONIZATION IN AUTOLYTUS VARIANS. 287 



insertion of the dorsal cirri to a position almost dorsal to that 

 of the setae. 



The head of this stolon has also assumed a different appear- 

 ance, and in a dorsal view has attained the size and shape of 

 the head of the Polybostricus. The anterior eyes have shifted 

 laterally and now occupy a position very similar to that repre- 

 sented in PI, XIII, Fig. II. The posterior eyes have been 

 carried forward to nearer the anterior margin of the head and 

 have increased considerably in size. The appendages of the 

 head have undergone no changes save an increase in length. 

 The buccal segment is now visible dorsally as a narrow seg- 

 ment considerably less in transverse diameter than the head 

 and very indistinctly separated from it. The dorsal tentacular 

 cirrus has increased very much in length, while the basal por- 

 tion has increased to a thickness greater than the dorsal width 

 of the buccal segment. The ventral tentacular cirri have 

 attained a length about equal to that of a dorsal cirrus. 



Stolon 6 represents the stage of advancement shortly before 

 the stolon is separated from the chain. As compared with the 

 preceding stolon the most striking change is the still greater 

 increase in the size of the parapodia and the presence of swim- 

 ming setae in all the parapodia except the three anterior. The 

 increase of the parapodia in thickness as well as in length has 

 given the posterior three-fourths of the stolon a more compact 

 appearance, thus making the distinction between the three 

 anterior and the posterior segments very much greater. The 

 larger parapodia are directed backward still farther, and in this 

 way a considerable space is left between the third and fourth 

 pair of parapodia. In an anterior view of such a parapodium 

 it will be seen that the different parts of this appendage have 

 assumed the appearance of those of a parapodium of a free- 

 swimming individual ; the dorsal ramus extending somewhat 

 beyond the ventral ramus and containing at its extremity a tuft 

 of long, slender swimming setae ; the dorsal cirrus inserted 

 some distance in from the insertion of the setae ; the ventral 

 ramus ending in a small tubercle containing a tuft of setae ; 

 while posterior to this tubercle the two rami unite to form a 

 broad plate made up by the musculature of this appendage. 



