REPAIRS AND REGENERATION 173 



provided with an entrance and an exit for the 

 water. 



To this succeeds a small connecting body 

 portion which contains part of the intestines 

 and finally there is the so-called intestine-sac 

 with stomach, intestine, heart , reproductive 

 organs, etc. If we divide the body of a Clavel- 

 lina at the level of the connecting portion, so 

 that the gill-basket and the intestinal-sac are 

 separated from one another, either or both of 

 these two portions can in three or four days 

 complete itself into an entire organism, since 

 by means of true regeneration proceeding from 

 the incision, the gill-basket makes itself an 

 intestinal-sac and the intestinal-sac a gill- 

 basket. 



With this process we have already become 

 familiar, for it is the kind of thing which we 

 have studied in the Hydra and in the earth- 

 worm, but the process of reconstruction some- 

 times takes place in quite a different manner, 

 and this is especially the case in smaller indi- 

 viduals. In these cases reconstruction begins 

 not by a process of renewal but by one of 

 regression. 



The organisation of the gill-basket, its 

 ciliated clefts, its openings, etc., all gradually 

 dwindle away. At the end of five or six days 

 no more organisation is to be seen in these 



