SOME PUGET SOUND ASCIDIANS. 595 



destroyed in the one case and not in the other. To be sure, it 

 is possible that the color increases with age, but this is not 

 usual with ascidians. 



The internal structural differences that do not seem explicable 

 on the supposition that they are due to differences in age alone 

 are the following : The tentacles are more numerous in C. 

 deani than in C. siipcrba, they being about twenty-four in the 

 former and eighteen in the latter. In species in which these 

 structures are small and very numerous, such a difference in 

 number as this could not be considered as of great consequence ; 

 but where the number is small and the tentacles themselves are 

 large, the difference certainly is of considerable importance, 

 particularly since the larger number is found in the supposably 

 younger specimens. 



The much more highly coiled condition of the hypophyseal 

 mouth in C. siipcrba can, I think, hardly be considered as due 

 to differences in age, although it must be admitted that the 

 differences here are in the direction that would be expected on 

 this supposition. But, judging from what we know of other 

 ascidians, we are not warranted, I think, in believing that differ- 

 ence so great in this respect as that here found is to be thus 

 accounted for. 



Again, the differences in the branchial sacs and the accessory 

 dorsal languets in the two forms are too great, I believe, to be 

 explained away on this hypothesis. Compare figures i8 and 

 22, also 17 and 23. 



The question of whether the CyntJiia coriacca of Stimpson 

 '64 is the species now under consideration must, I am con- 

 vinced, with the data now at hand, be answered in the negative. 

 Stimpson describes his species as being " smooth, and scarcely 

 at all wrinkled." This statement clearly means that it is not 

 only without wrinkles, but also that it is without asperities. It 

 is true that the papillae of our species are very small, but I can 

 hardly believe they could have escaped so good an observer 

 entirely. The branchial sac, the author says, " has about the 

 same number of folds as the preceding species," referring to 

 Styela glbbsii, which, he says, has 10 folds. As our species has 



