galloway: non-sexual reproduction in dero vaga, 117 



3. Position of the Bud zone : Primary and Secondary. 



In such a worm, if the food supply be normal, a budding zone is 

 formed some distance anterior to the preanal or segment-forming zone. 

 Bourne ('91) has suggested that the segment at which bud formation 

 takes place is probably constant for each species. This is certainly not 

 the case here, at least not for the asexually produced zooids. I am not 

 yet able to say what may be true of the sexually derived individuals, for 

 I have not as yet discovered how, if at all, the sexually produced zooid 

 may be certainly distinguished from the non-sexually produced forms. 

 That probably can be settled satisfactorily only by rearing young worms 

 from fertilized eggs. 



The cellular activity accompanying budding, it is to be observed, in- 

 volves only one segment, and the plane of separation is always midway 

 between dissepiments. The position of this budding segment in the 

 individuals which I have examined is variable within certain narrow 

 limits. It may occur as far forward as the 16th and as far backward 

 as the 21st setigerous segment. The following table, representing obser- 

 vations upon about three hundred individuals, gives in percentages the 

 frequency of occurrence in these two and the intervening segments. 



TABLE I. 



Table II. is a record of observations upon the position of the budding 

 segment in successive generations. 



TABLE II. 



