82 Charles W. Hargitt. ' » 



these organs are readily regenerated, and that in a state of nature 

 as well as under the artificial conditions of the laboratory. An 

 examination made with the hand lens on June 2d, or only four 

 or five days following the operation, showed the first indication 

 of regenerating rhopalia. As the organ first makes its appearance 

 it is a very minute papilla-like body, and in these cases at the 

 inner, or upper edge of the notch made by the incision. Ex- 

 amined under the compound microscope the papilla appears as 

 a minute, solid bud growing out from the terminal region of 

 the radial canal, though it does not at first seem to be a direct 

 outgrowth of that organ. Very soon, however, there is established 

 a direct connection with the canal, and it is quite easy to dis- 

 tinguish the circulation of the gastric fluid in the little bud, which 

 becomes definitely vesicular, as shown in Figure 2. The growth 

 of the organ, after its vesicular stage is established, is quite rapid 

 and there can soon be distinguished the thickening of the terminal 

 portion to form the lithocysts. Coincident with this stage of de- 

 velopment there is discernible the development of the new hood 

 and lappets, accessory organs, and as will be shown in connec- 

 tion with a study of the histology of these organs, the correspond- 

 ing development of the so-called olfactory and ocellar pits. 



In connection with the present series the following experiments 

 were made with a view to demonstrate that, not only in form but 

 in function, the new rhopalia were perfect organs. From one 

 of the specimens just described in which three rhopalia had been 

 originally excised the other five were excised on June 5th, or seven 

 days after the original experiment. If the three regenerated 

 organs had not yet attained to functional utility the effect of re- 

 moving the others would, of course, result in the typical paralysis, 

 as in the first experiment already described. As was anticipated, 

 the careful removal of all the rhopalia except the three regenerated 

 ones did not in the least interrupt the normal rhythm or activity 

 of the creature, save to act as a stimulus to quicken it, as already 

 cited in connection with a previous series. This experiment was 

 repeated upon several others of this as well as subsequent series, 

 and always with the same results, except in a single case which 

 may as well be cited in this connection, though coming under later 

 experiments. 



