574 bulletin: museum of comparative zoology. 



generated structure, for great care was taken after each operation to 

 make sure that the original brain had been removed. The regenerated 

 brain consisted of a central region, containing relatively few cells, and 

 a peripheral region, composed of closely packed cells which partially 

 surrounded the central mass. The brain periphery was not sharply 

 demarked from the surrounding tissue. A pair of regenerated nerves 

 ran forward, as in the normal worm, from the base of the brain. One 

 nerve ended at the deep boundary of the epidermis on the dorsal wall 

 of the invagination described below. Both of them plainly showed 

 a fibrous region, which stained like the central part of the brain. 



A deep, horizontally elongated invagination (stmd.) occurred near 

 the tip of the regenerated cone. Three lines of evidence clearly 

 showed that it was a stomodeum. (1) It had the characteristic shape 

 of a stomodeum. In a horizontal direction its greatest dimension 

 was about sixteen times that in the plane (sagittal) of the sections. 

 Median sections of the invagination resembled the median section 

 of a funnel. Stomodea in the control animals had approximately the 

 same shape. (2) It occurred in the normal position for a stomodeum, 

 i. e., near the tip of a regenerated cone, with its antero-posterior axis 

 pointing toward the nerve ring formed by the brain, the connectives, 

 and the ventral nerve cord. (3) It is very highly improbable that 

 such a deep, slit-like infolding could be merely a wrinkle, in the new 

 epithelium, caused by the contraction of the regenerated circular 

 muscles when the worm was killed. The invagination probably 

 could not have been produced in this way unless the surface of the 

 regenerated region were originally flat or concave, whereas, owdng to 

 internal pressure of the body fluid it must have been more or less 

 convex, so that any contraction of the regenerated circular muscles 

 would most likely have caused an elongation, instead of a buckling 

 inward, of the cone. The infolding was certainly a stomodemn. 



Number 359. Eisenia foetida (Savigny). Thirty days after the 

 operation the closed digestive tube was five segments from the healed 

 anterior end of the worm. At this end an invagination Avas found in 

 the regenerated tissue. The close proximity of this infolding to the 

 regenerating end of the nerve cord, its shape (as compared \nth 

 stomodea in the regenerating control animals), and the absence of 

 any evidence that it could have resulted from muscular contractions, 

 clearly indicate that it was a stomodeimi. It is a significant fact 

 that this stomodeum developed, not only in the absence of the diges- 

 tive tube at the regeneiating end, but before the brain and connectives 

 had formed. 



