3i6 MENSCH. [Vol. XVI. 



containing from 40 to 48 setigerous segments, all of which, 

 with the exception of the anal, are similar in structure, and 

 many of which have reached a stage of development equal to 

 that of the segments of a chain-bearing parent stock. It con- 

 sists in a thickening of the ectoderm of one of the segments 

 posterior to the i8th to 38th, and the subsequent development 

 of the head in a manner very similar to the development 

 of the head in the embryonic segments of the chain. The 

 appearance of the head at once marks a division of the indi- 

 vidual into an anterior parent stock, and a posterior stolon 

 formed of segments originally belonging to the young indi- 

 vidual and hence formed in a manner different from the forma- 

 tion of the stolons of the chain. The manner in which this 

 stolon is formed has been described as that of fission {scissi- 

 parite, de St. -Joseph) in forms in which the production of a 

 single stolon is followed by its separation and a subsequent 

 regeneration of separated parts. In chain-bearing forms, how- 

 ever, this so-called fission, besides producing a stolon that is 

 different from the stolons separated from the chain, does not 

 consist of the separation of the stolon after it has matured; 

 but in the course of the formation of the head and buccal seg- 

 ment, new tissues and later new segments begin to appear 

 between the segment upon which the head has been formed 

 and the segment anterior to it. In this way the stolon is car- 

 ried back just as is the case in the maturing stolons of the 

 chain, and finally becomes separated as the first stolon of the 

 newly formed chain. Before the stolon has separated, the new 

 segments may have become sufficiently numerous and their 

 development advanced sufficiently far to show the presence of 

 one or two distinct stolons similar in appearance to the young- 

 est stolon represented in PI. XIII, Fig. 6. Subsequently, while 

 these young stolons are maturing, the chain is elongated by the 

 addition of new segments and the development of new stolons 

 in the manner described by de St.-Joseph and Malaquin in similar 

 chain-bearing species as that of budding (bourgeo7inement). 



Stolonization accordingly makes its appearance in the young 

 so-called asexual individuals in the formation of a single stolon, 

 by a process somewhat similar to that of fission in chainless 



