162 ESTIVATION OF BOTRYLLOIDES GASCOI DELLA VALLE. 



was represented only by portions of the stolons containing stored reserve matter 

 and an epicardial septum without buds. In conclusion the authors stated that the 

 accumulation of reserve matter should be interpreted as a normal process permitting 

 the latent life of the colony for a certain time. 



I have no fault to find with either of these two conclusions; and although they 

 appear somewhat contradictory, the aestivation of Botrylloides might be included 

 in either of the two categories. It is, however, necessary to be more precise in defin- 

 ing what we mean by latent life. Certainly, when compared with the fife of the nor- 

 mal colony, the activating Botrylloides and, still more, the hibernating Clavelina 

 may be said to be in a dormant condition, or to have only latent life. On the other 

 hand, if by latent life is meant the condition that obtains in seeds or in a dried rotifer 

 it would not be justifiable to apply the term to these cases, for in Botrylloides we 

 always have a vigorous circulation kept up by the ampullae, and the statement of 

 Giard and Caullery that, in the Clavelina stolon, certain cells seem to be multiplying 

 shows that they think that there is considerable metabolism going on. Indeed, « I 

 think it extremely probable that if the hibernating stolons of Clavelina could be 

 induced to grow on glass where they' could be carefully examined alive, it would be 

 found that contractions of the ectoderm cells are maintaining a circulation. 



The power of executing slow contractions seems to be quite widely distributed 

 among the epithelia of the Ascidians. Thus not only do the ampullae and blood- 

 vessels contract regularly in Botryllus and Botrylloides, but Delia Valle (:00, :00 a ) 

 has found that at times the ectoderm of the vascular projections of Diplosoma listeri 

 and Styela plicata execute vigorous contractions. I have also observed in Botryllus 

 that tissues, which were not destined by nature to propel the blood, behave like the 

 ampullae when subjected to similar conditions. Thus, in one experiment a young 

 bud was isolated with a few ampullae, but, instead of developing itself, its buds were 

 stimulated to rapid growth, while the original bud became a hollow chamber which 

 kept up a vigorous circulation by slow contractions of its walls. In another case 

 both buds were cut away from an adult zooid which was left attached to some blood- 

 vessels. Here, too, the zooid was transformed into a blood-pumping organ. If the 

 ectoderm of the hibernating Clavelina stolon maintains a circulation, as in these 

 other cases, there would be still less justification in comparing its condition to the 

 latent life of seeds. 



Concerning the other conclusion of Caullery, that the degeneration of the colony 

 is due to its senescence, and is not a direct response to the environment, I believe that 

 it is correct for Botrylloides as well as for the species that he studied. But, as already 

 indicated (p. 161), my data are not sufficient to prove this point. In the case of 



