128 SIDNEY F. HARMER. 



Tubulipora the entire colony cannot be looked upon as an 

 individual of the third order to the same extent as can that of 

 Lichenopora; but a certain amount of individuality may be 

 recognised in each of the ovicell-bearing lobes. The fertile 

 zocecium is, in fact^ differentiated at a very early stage in the 

 development of a lobe. This may be understood by reference 

 to fig. 1, in which a young ovicell is beginning to develop at 

 the right of the figure. The development of the first ovicells 

 of the colony begins in T. plumosa in the immature stage 

 which was considered by Thompson and Johnston as the adult 

 condition of this species. 



The phenomena of the selection of the fertile zooecia are 

 probably more primitive in Tubulipora than in Licheno- 

 pora, in which the differentiation of the ovicell may have 

 been thrown back to an early stage in the development of the 

 colony_, in correlation with the high degree of individuality 

 which is possessed by the entire colony in that genus. 



Internal evidence that the ovicell is at first a zooecium is 

 afforded by the invariable presence in it of a brown body, 

 indicating the previous existence of a polypide. This may be 

 called the "fertile brown body/^ as in the case of Licheno- 

 pora. 



In the latter the fertile polypide is not the first inhabitant of 

 its zooecium, as is indicated by the simultaneous presence in it 

 of a brown body, a functional polypide, and an embryophore. 

 In Tubulipora, on the contrary, the first polypide of the 

 fertile zooecium becomes fertile, and no new polypide is deve- 

 loped in the normal ovicell after the first brown body is formed. 

 In cases of abnormal development, however, the entire embryo- 

 phore may degenerate, and a new polypide-bud may make its 

 appearance. In a single case only I have found a brown body 

 (in addition to the normal brown body) on the proximal side 

 of an embryophore in stage E. This may be interpreted as 

 evidence of the degeneration of a polypide before the formation 

 of the definitive fertile polypide. 



It is not easy to obtain evidence showing the exact stage 

 at which degeneration of the fertile polypide takes place in 



