160 AESTIVATION OF BOTRYLLOIDES GASCOI BELLA VALLE. 



have been unevenly distributed. Consequently in some parts of the colony there was 

 not enough food to stimulate the buds to any growth, and they remained dormant. 

 In other parts the food was sufficient to start development, but not to keep it going 

 for long, and the buds soon stopped growing and began to degenerate. On the 

 growing edge, however, the food was sufficient, and it was here that the buds devel- 

 oped most normally, and ultimately reconstructed a vigorous colony. It is to be 

 noted, however, that the smaller the part of the colony we observe the more uniform 

 will be the conditions in it, and actually it was found that buds which were near 

 together almost always developed and degenerated together. 



C. THE SYSTEMS. The third difference between the normal and rejuvenating 

 colony concerns the systems. Normally systems are present most of the time, but in 

 the rejuvenating colony they formed the exception. One reason for this was undoubt- 

 edly the fact pointed out before that the period of the adult existence of the zooids 

 was so much shortened. I am inclined to believe that this is the sole reason, and 

 that buds in the Botryllidae do not tend to form systems at all until about the time 

 when they open their siphons and become adult zooids. On the other hand it may 

 be that there was a tendency for the buds in the rejuvenating colony to form a system 

 before they reached the adult condition, but they were prevented from doing it by 

 the rapid movement that they were undergoing in connection with the rest of the 

 growing edge. Whatever the cause may have been, however, it is certain that in 

 normal colonies one does not see masses of closely crowded buds with their branchial 

 ends all pointing one way and no indication of a s} ? stem, such as have been represented 

 in Figure 8 and especially in Figure 1. 



3. Color. Delia Valle ('77) describes the zooids of B. gascoi as being violet in 

 certain definite regions and lemon-yellow or white in others. The ampullae are lemon- 

 yellow. Before aestivation the colony here described, which was closely similar in 

 color to other colonies brought into the laboratory, corresponded in general quite 

 well with Delia Valle's description except that it was also colored red in some places. 

 The young buds were yellow, and the ampullae were both violet and yellow. At the 

 time when all the zooids died, leaving the colony differentiated into a lilac and a yel- 

 low part, the blood-vessels and ampullae of each part had the characteristic color. 

 When the buds began to appear in the rejuvenating colony they and everything else 

 were colored a uniform yellow; and this color was retained by all portions of the 

 colony as long as it was observed. The rejuvenated colony was exactly like the 

 original one in every respect except that of color. But in this regard it did not 

 resemble B. gascoi at all, but corresponded closely to Botrylloides luteum von Drasche 

 ('84). In its transparency, which allowed the stigmata to be easily seen in life, it 



