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



Piece II. — In fair condition; it has been in the aqua- 

 rium for one or two weeks. Color is Van Dyke brown 

 with streaky yellow coats, 



September 16. Piece I.— In fine condition. The color 

 differences observed on the eighth still persist, but the 

 coats are not so distinct. 



September 26. Piece I. — In fair condition. On the 

 right the coats are better developed than on the left. 



October 11. Piece I. — Badly overgrown with calca- 

 reous worm-tubes and hydroids, but still in fair condition. 

 The color of the coats varies from orange to greenish 

 yellow. The ground-color varies from a light to a very 

 dark brown. 



4. Variations among Colonies Produced by the 

 Same Mother. 



These variations are more extensive than any previously 

 mentioned, and in addition, are often characterized by a 

 decided discontinuity. The variation in the species as a 

 whole, however, is continuous, all gradations being en- 

 countered; so that a continuous series seems to be pro- 

 duced by the summation of the variants of a large number 

 of families, each of which normally consists of a discon- 

 tinuous series. 



The colors of the zooids are made up of three con- 

 stituents: — 



(a) The ground-color. 



(b) Some of the lines and spots making up the color pat- 

 terns in some zooids. In the main these are the markings 

 discussed on page 145, and their position seems mostly 

 to be due to underlying blood-vessels. They are usually 

 quite variable in the same colony, and disappear entirely in 

 old age. 



(c) Other color markings which cannot be distinguished 

 from those of class (b) by inspection, but behave very 

 differently from them so far as variation is concerned. 



