Sonu" Pliciioim-na of Regoncration in Linmodi iliis aiul rclalcd Foriiis. 413 



tcnsion of tlio luusrular cuat aiul Xhc clil(jru*f()gue ovcr thc iiew intcs- 

 tiiie. Tlie miusculature of the intestinal wall is so closely surrounded 

 bv tlu> perivisceral blood vessel that even in the uninjured parts it is 

 rather difficidt to distinguisli the two. By close Observation one can see 

 the sniall, dark nuclei of the fibers in intiniate contact with the outer 

 peripheral surface of the entoderm either singly or in groups and about 

 theni the spindle shaped cell bodies. In the many articles that have 

 beeu written concerning the histogenesis of regeneration very little 

 lias been said about the origin of the intestinal musculature. Abel (02) 

 discusses the question very briefly for Tubifex and says these muscles 

 are derived froni the sarae material as are the longitudinal muscles 

 cf the body wall (i. e. cells of ectodermal origin) groups of such (;ells 

 being applied to the outer wall of the intestine and transformed to 

 nuiscle. IwANOAV (03) gives a somewhat more detailed account of the 

 process in Lumhriculus and derives the longitudinal fibers from the 

 visceral wall of the coelomic sacks, certain cells of which, v/ith sjnall 

 dark nuclei, become applied to the wall of the intestine and are trans- 

 formed into muscle fibers. Iwanow believes the coelomic sacks are 

 of mesodermial origin. From my owii observations it is evident that 

 where the developing septa join the intestine some cells with small 

 nuclei migrate to the intestinal wall, become closely applied to it, 

 elongate and are transformed into muscle fibers. This description 

 applies only to normal regeneration. In the case under discussion, 

 where the intestine does not come in contact with other tissues, the 

 origin of the musculature is different. In certain cases the proximity 

 of the intestine to the Strand gives the Impression that some of its 

 cells may be concerned in the formation of the new intestinal mus- 

 culature. However it is to be seen that the Strand splits at the tip 

 of the intestine and passes up along its sides leaving a short space 

 sejiarating the two (Fig. 7). The Strand, therefore does not give rise 

 to the intestinal muscles. These are derived from the old intestinal 

 musculature through increase and migration of the latter's cells. In 

 the vicinity of the point from which the new intestine grows some of 

 the nuiscle cells detach themselves from the entoderm and migrate 

 toward the new portion of the intestine (Fig. 7). Both before this 

 and in course of migration a few may be seen dividing, which so far 

 as observed, is done araitotically. Along the sides of the iicav intestine 

 tliey again attach themselves and form its musculature. 



The chlorogogue along the new intestine is also due to a migration 

 of the old cells. At first these do not keep pace with the growth of thc 



