74 SIDNEY F. HARMER. 



The question is further complicated by difficulties in deciding 

 which names have the greatest claim to be assigned to parti- 

 cular species. 



Before proceeding to the accounts of the species the scope 

 of the paper may be stated, I have given diagnoses of two 

 Northern species, one of which I believe to be new, and of all 

 the forms ordinarily recognised as British species of Tubuli- 

 pora, with the exception of T, lobulata, Hassall. 



I have not had a sufficient supply of this supposed species to 

 enable me to come to any clear conclusion about it. Many of 

 the colonies which I have found on shells in the deeper Ply- 

 mouth dredgings (20 — 30 fathoms) agree well enough with 

 Hincks's description of this form. I have also seen similar 

 specimens from the Liverpool district, kindly lent to me by 

 Professor Herdman; but I have not been able to examine un- 

 injured mature colonies. In the absence of perfect ovicells, 

 it is possible that some of the specimens supposed to be T. 

 lobulata may be worn examples of other species of Tubuli- 

 pora. I prefer, therefore, to express no opinion with regard 

 to this form. 



The paper is divided in the following way : 



I. Structure of the colony and of the ovicell. (The terms 

 " ooeciostome'^ and "ooeciopore" are here proposed.) 



II. History of the species and genus. 



III. Synonymy, diagnoses, and accounts of the species. 

 (New species, T. a pert a.) 



IV. The nature of certain vesicles found in the tentacles and 

 other parts, with a few statements relating to the budding and 

 the structure of the adult zooecium. 



V. Description of the development. (The terms *' axial 

 lobe" and "lateral lobes" are here proposed.) 



VI. The morphology of the internal parts of the ovicell. 



I. Structure of the Colony and of the Ovicell. 



A colony of Tubulipora, as of other Cyclostomes, takes 

 its origin in the well-known circular primitive disc (PI. 8, 



