44 CALIFORNIA ACADEMY OP' SCIENCES. 



chanical means, that this micrht be due to a still closer 

 crowding together of the zooids, and that sections would 

 reveal planes of contact between the tests of the different 

 individuals. However, such examination proves beyond 

 the possibility of a doubt that no such contact planes 

 exist. As is shown by fig. 5, pi. i, which is drawn 

 from a section of one of these colonies, the test is con- 

 tinuous from one zooid to another, entirely without inter- 

 ruption. 



From the facts thus presented, the question arises, has 

 this fully compounded condition been produced b}^ such a 

 crowding of the adult zooids of the colony that the tests 

 have become fused by mutual pressure, aided, perhaps, 

 by the constant renewal of the test by growth? Is 

 it not possible that since these individuals of a colony 

 have a common blood svstem, their tests ""row toorether 

 when brought in contact, after something the same fashion 

 that the severed surfaces of a wound grow together when 

 brought in contact? And it is possible that the process 

 may be assisted by the slight irritation that would be pro- 

 duced on the surfaces in contact. One fact seems to 

 favor such a view. Colonies may be found in which the 

 individuals, though each possessing its own test, are still 

 so closely pressed that they adhere to one another to such 

 an extent as to admit of separation only with considerable 

 force. That complete obliteration of the plane of contact 

 ever takes place in this manner, I have, however, not 

 been able to demonstrate. But even if the compound- 

 ing is ever produced in this way, or was so produced 

 phylogenetically, it is very easy to show that it is not now 

 so produced ontogenetically. The developing individuals 

 in these colonies are from the beginning as completely 

 buried in the common test as are the adults. Figure i 

 represents a small portion of the tip of one of the much 



