No. 2.] THE STOLOX IN AUTOLYTUS. 91 



the stolon are of comparatively infrequent occurrence. The 

 position of the stolon is very constantly on the thirteenth seg- 

 ment. In more than 200 specimens of P. ornata examined, 

 not more than nine were found in which the stolon was attached 

 to any other than the thirteenth segment; of these, six were 

 found to bear the stolon on the fourteenth segment, while in 

 three it was borne on the twelfth segment. In a single instance 

 I have found the stolon as far forward as the eleventh segment. 

 In all cases the variation was among individuals which bore 

 male stolons. 



P. tardigrada shows even less variation than P. ornata. In 55 

 individuals examined, not a single case of variation was observed. 

 Out of 1 10 individuals examined, Andrews (Proc. U. S.Nat.J\Ins., 

 Vol. XIV) obtained three specimens with the bud attached to 

 the fourteenth segment. 



Variations in the position of the stolon in the two species of 

 Proceraea would accordingly be confined almost exclusively to 

 occurrences of the position of the stolon either immediately 

 anterior or posterior to a fixed segment, the posterior position 

 being the most frequent form of variation. 



In A. cornutus variations in the position of the bud are of 

 still less frequent occurrence. Out of 178 specimens examined 

 at a time when the forms were most abundant, not a single case 

 of variation was observed. I have, however, found specimens in 

 which the stolon was attached to the twelfth segment, but, as 

 compared with Proceraea, such occurrences are very rare. 



A further proof of the more constant occurrence of the bud 

 on the thirteenth segment in this species is the fact that in 

 individuals in which mutilation or severance of segments anterior 

 to the region of budding has occurred, in the subsequent regen- 

 eration of new segments, the bud will not, as I have observed 

 in Proceraea, develop its head from the tissues of the most 

 anterior regenerated segment, but will first of all regenerate 

 the lost segments of the parent stock, and following these pro- 

 duce the bud. The accompanying figure represents a specimen 

 in which all the segments of the parent stock posterior to the 

 eleventh were amputated and have been replaced by a series of 

 new segments. The bud, instead of taking its origin in the 



