410 F. H. Krecker, 



poiiits is the regularity exliibited in tlie arrangement of the fibers. 

 Except where interfered with by obstructioiis tliey do not form an 

 unordered mass extending in all directions but a Strand extending along 

 one axis. It is very probable that the free ends of the fibrils become 

 attached to some point within the coeloni and that then the extension 

 and contraction of the animal's body exerts a strain lipon them which 

 holds them in a more or less compact Strand. The formation of such 

 Strands as have been described has not been noted in normal regene- 

 ration and its absence there is to be accounted for by the contiimal 

 presence of the intestine which occupies the coelom and is close to the 

 wound, thus preventing the muscle fibers from wandering. To a 

 ccrtain extent the same is true in those instances where a solid plug 

 of chlorogogue cells fills the coelom, iinder which circumstances com- 

 paratively little muscle appears in the plug. 



The Intestine. 



The initial steps in the healing of the intestine are in some respects 

 similar to what occurs in the body wall. As soon as the intestine has 

 been severed the part remaining in the body is retracted to its normal 

 Position. The lips of the wound then contract and meet in the me- 

 dian line thus completely closing the intestine. About the end of the 

 intestine are collected entodermal cells which have been torn off by 

 the Operation, blood, loose chlorogogue and leucocytes (Fig. 6). In 

 the course of a day the entoderm becomes so thoroughly knit together 

 that there is little indication of an injiiry. The blood vessels are also 

 quickly repaired and closely invest this region. At the anterior body 

 levels where the intestine falls to regenerate this is the permanent 

 condition. In such cases even after four weeks there is no trace of 

 growth; the intestine is rounded at the jDosterior end and there is no 

 opening. The epithelial lining of the intestinal cavity appears normal; 

 and there is no indication of ceU division; the cells are not enlarged 

 nor have they prohferated and formed a plug. The outer, muscular 

 layer of the intestinal wall extends completely around the posterior 

 end and, frequently, surrounding this is the large dorsal blood vessel 

 which becomes considerably convoluted and enlarged to form more 

 or less of a sinus (Fig. 5). It connects with the ventral vessel and in 

 additions gives off small branches which run down to the posterior end 

 of the body. 



When we consider the causes for this absence of entodermal re- 

 generatioji there seems to be no reason from a histological viewpoint 



