GALLOWAY: NON-SEXUAL REPRODUCTION IN DERO VAGA. 119 



simulates the condition of Aj 3-7 (Fig. I.), and consequently that the 

 second new individual, which is thus to be produced at the posterior 

 end of A (Fig. T.), arises from a region which was undifferentiated during 

 the first budding. The half-segment 4 (Fig. I.) produces a prostomium 

 and four cephalic segments, B, 1 (Fig. II.). At the same time, the indiffer- 

 ent preanal zone, 6 (Fig. I.) is adding segments to the region 5, which 

 before these additions embraces a small but variable (5-10) number of 

 body segments. Since the budding in no case takes place in a segment 

 so near the head as the tenth body segment, it follows that this must 

 occur in the undifferentiated region 6 (Fig. I.), and consequently it is 

 true for the posterior as well as the anterior zooid that, when a new 

 budding takes place, it occurs in a zone that was undifferentiated during 

 the preceding process of budding. 



4. Relation of Budding to Formation of Segments. 



If the worms are well nourished, the secondary divisions often com- 

 mence before the first is completed. A condition of this sort is shown 

 in Plate 1, Fig. 3. In such instances the secondary bud (z^) in each 

 zooid lies within the limits, either of the indifferent zone (anterior zooid), 

 or of still incompletely differentiated segments (a condition more usually 

 found in the posterior zooid). 



There is thus shown to be a close relation between the process of 

 budding and that of forming new segments. For the material which 

 is destined to subserve the process of budding is at one time an indis- 

 guishable part of the zone (preanal) the posterior part of which is a con- 

 tinuous source of new segments. In every case the budding zone, on its 

 part, gives rise to two segment forming regions : a posterior, which is 

 normally limited to the production of four segments beside the cephalic 

 lobe ; and an anterior, which never loses the power of forming new seg- 

 ments, since some of the segments thus produced, or at least one of 

 them, retain the capacity of forming a new bud, by which the process is 

 repeated and the power perpetuated indefinitely. In other words, the re- 

 lation of the two processes in this worm is such as to lend support to the 

 view that here budding is a specialized form of normal segmentation. 

 The cycle of procedure occurs just as if, in the formation of segments 

 from the indifferent preanal zone, there were deposited at a certain stage, 

 in one or several segments, materials w^hich are capable under appropriate 

 circumstances of giving rise to indifferent tissue and to new segments. 



This fact allies itself with what is known of regeneration of lost parts. 



