Somo Phcnonii'ui <>f ReficiKTatioii in Liiiinudiilus and irlatcd Fonns. 441 



tlie worm, especially tlie niusculature and the peritoiieum, and they 

 form the mesodennal structures of the regenerating portioii. Per- 

 haps V. Wagner inchided these among his »Reiiarationszellen «, parti- 

 culaiy since, as he says, »dieselben . . . bieten, wenn sie aus dem Epi- 

 thel auswandern, die mannigfaltig.-^ten Formen dar«. The »Granu- 

 lationsgewebe« of which RiEVEL speaks in Nais is probably also re- 

 presented by these cells. According to him the »Granulationsgewebe« 

 comes from the »vorhandenen Mesenchymelementen« and forms some 

 of the mesodennal structures. 



By examining individuals killed at successive intervals after au 

 Operation one can easily follow the steps in the redifferentiation of 

 tlie old mesoderm into the mesoderm of the new part. I studied spc- 

 cimens of Limnodrilus and Tuhifex killed two, five, seven, twelve 

 and twenty-one days, respectively, after the Operation and gave my 

 attention mainly to the development of the musculature in the body 

 wall. Up to the fiftli day after the Operation practically no new meso- 

 derm had been formed, the changes which occured consisting chiefly 

 in the disintegration of the old mesoderm. The free cut edges of the 

 body wall musculature fray out, so to speak, much as they do at the 

 posterior end of an individual from which some of the intestine has 

 been removed (Fig. 25 and 26). In the forms under consideration 

 the nmscle fibers are long and spindle shaped. AVhen set free by the 

 disintegration of the muscles these cells gradually lost the contractile 

 substance. They wander about freely in the coelom, the general di- 

 rection of the movement being toward the anterior end of the worm. 

 In this way the coelom of this region is soon occupied by numerous 

 more or less spindle shaped cells with a slightly granulär cytoplasm 

 and large nucleus containing a deeply staining nucleolus. In all pro- 

 bability, peritoneal cells and connective tissue cells are also mingled 

 with these wandering muscle cells. In the confused state of the cells 

 at this time it is frequently hard to distinguish between the various 

 types. In addition to the migration of cells the mass of cells in the 

 coelom is also increased by the mitotic division of those already present. 

 In Lumbricus hereculeus a somewhat similar condition was found. 

 The specimens examined were not used priraarily to follow the changes 

 of the mesoderm and consequently whcn they were killed these changes 

 were in an advanced state, still it was possible to see that the process 

 in this form does not differ essentially from that found in Limnodrilus 

 and Tubifex. The usually compact fibers of the musculature of the 

 body wall were loosely knit together in the neighborhood of the new 



