278 MENSCH. [Vol. XVI. 



sented in this figure, four such segments are present. In all 

 cases, however, whether three or four segments be present, the 

 first and the last are a little larger and more developed than 

 the intervening segments. 



The beginning formation of this stolon is more evident in a 

 slightly older series of this kind, with four segments, as is rep- 

 resented in PI. XIII, Fig. 7. Segments i, 2, and 3 represent 

 the three appendage-bearing segments of Fig. 6 (St. A). Seg- 

 ments I and 3 have increased in size and bear lateral append- 

 ages of about equal size, while segment 2 has increased less 

 and has smaller appendages. Between segments 2 and 3 a new 

 segment has made its appearance and presents the same embry- 

 onic characters as do segments i and 2 in the embryonic region 

 of Fig. 6. 



In such a series as is represented in Fig. 7 there are pres- 

 ent all the segments necessary for the formation of the differ- 

 ent regions of a mature stolon. Of these, segment i becomes 

 the first setigerous segment from which will be developed the 

 head and the buccal segment ; segment 3 forms the anal seg- 

 ment ; and segment x represents the region of new growth 

 which contributes to the elongation of the stolon. The origin 

 of segment x, as we shall see in the study of a section of this 

 region, appears to be from the anal segment and is not depend- 

 ent upon any contribution from segment 2 in the process of 

 its development. In this way segments i and 3 become the 

 important factors in the development of the stolons, while seg- 

 ment 2 remains as an indifferent zone which is constantly 

 being increased by the addition of new segments posteriorly, 

 Malaquin (9) in describing the development of the stolon in 

 Myrianidae lays great weight upon the importance of the anal 

 segment (Pygidium) so far as its early appearance is concerned, 

 but pays less regard to the part it plays in the formation of the 

 embryonic segment {x) of this stolon, a fact which I regard as 

 of no little importance. 



The origin of this stolon would then be by (i) the successive 

 outgrowth from the last segment of the parent stock, or seg- 

 ment of proliferation, of three embryonic segments similar to 

 the three segments of stolon A in Fig. 6, followed by (2) the 



