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



as the summation of the characters of the zooids. Morpho- 

 logically the colony is not the sum of its zooids, for: — 



1. The colony consists of zooids plus the test and the 

 common vascular system. 



2. The test is derived in part from the zooids, but prob- 

 ably its major portion is secreted by the ampullae of the 

 vessels. 



3. The common vascular system is not a derivative of 

 the zooids but of the larva. From the first the young colony 

 may be separated into embryozooid and the vessels with 

 their ampullae. And, though some vessels are derived from 

 the zooids, most of them are developed directly from the 

 vessels of the larva. 



The third of the -physiological characters, the coordination 

 in the growth and reproduction of the zooids, is also, in 

 great measure, if not entirely, dependent upon the common 

 vascular system ; for it disappears when a colony is cut in 

 pieces. Thus, it is seen that four of the eight characters 

 which distinguish the colony as a single individual are inti- 

 mately associated with the common vascular system. That 

 is, they are the result of the union of the parts into a common 

 mass, and are not dependent upon the common origin of the 

 parts. This is proven by the fact that they are all true of 

 the composite individual formed by means of fusion. They 

 can in no sense be considered as the summation of the 

 characters of the zooids, but pertain to the colony as a 

 whole. 



The other characters, however, the constant color mark- 

 ings of the zooids, the quality of the colony determining 

 fusion, and the system-forming force, apparently do not 

 depend upon the union of the parts into a common mass, 

 but do depend upon their common origin. They are, so 

 far as can be told, not changed in any colony by its fusion 

 with another one. It is, however, only as regards the color 

 of the zooids that we could expect to detect any influence 

 of one part of a composite colony on the other. Any similar 

 influence of one part on another affecting the normal size 



