140 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



and of the same food supply, and compete with Botryllus 

 for both. Of these, the second class is much more 

 important and harmful. 



It was only at Naples that any of the enemies proper 

 were encountered; but at one time they caused seri- 

 ous trouble, large portions of some of the colonies 

 being removed from the slides each day. The enemies 

 seem to have been crabs, for when the board with the 

 slides was removed from the bottom of the boat, to which 

 it had been attached, and left floating where none of the 

 animals crawling about on the boat could reach it, these 

 depredations ceased. In the aquarium, also, crabs were 

 found to remove Botryllus from the slides, and eat it with 

 avidity. The writer could not see that any preference was 

 evinced for any particular color of Botryllus; so it would 

 seem that their brilliant colors cannot be considered as 

 warning colors. When, however, Botrylloides rubrutn was 

 fed, pieces of the colony were at first detached, but were 

 not eaten, and later the colony itself was not molested. 

 Here, then, it might be said that there is a warning color, 

 associated with an unpleasant taste, but the case of Botryllus 

 makes it probable that even here the conspicuous color 

 has not been developed as a warning color. 



The mortality of the young colonies, especially of the 

 embryozooids, is very great. It was determined for three 

 lots of sister colonies.^ In the first (fourteen individuals), 

 only one, or seven per cent, lived beyond the sixth day; 

 in the second lot (seventy-five individuals), twenty-five per 

 cent were alive on the eighth day; and in the third lot 

 (fifty-nine individuals), seventy-four per cent were alive 

 on the ninth day, and fifty-seven per cent after one month. 

 Some of these colonies, consisting of an embryozooid or first 

 blastozooid, were undoubtedly removed bodily from the 

 slides by their enemies; but the greater part were found 

 still attached to the slides after decomposition had set in. 

 Thus, in the first and third lots, the numbers of young 



1 When the locality whence the colonies are derived is not stated, it is understood 

 that they were Naples, and not Woods Hole, colonies. 



