136 SYDNEY J. HICKSON, M.A., D.SC, F.R.S., F.Z.S. 



made. To give only one example to illustrate this point : — A specimen 

 in the Manchester Museum was named Millepora intricata, and, on 

 comparing it with the description of the species, I thought at first that 

 the name was correct. On breaking it into two pieces, however, I found 

 that the form it had assumed was due to the fact that it had grown 

 over a small piece of wood. 



In a still greater number of cases, however, the Millepores grow upon 

 the dead coralla of other Millepores or Madrepores or other white corals, 

 and then the difficulty of determining whether the form of the specimen 

 is due primarily to the living coral or to the one on which it has grown 

 becomes extreme. There is a large specimen in the collection brought 

 home from New Britain by Dr. Willey, of very irregular form, one part 

 of which has a form like that attributed to the species M. plicata, 

 another part to the species M. verrucosa, but a broken knob shows quite 

 clearly that a part of this great mass has grown over a dead coral. It 

 would consequently be quite impossible to determine with any degree 

 of satisfaction to which of the already-described species it belongs, 

 unless every knob and projection were broken off to see whether the dead 

 coral extends as a basis through the whole piece. 



In the second place, the immense amount of variation in form which 

 occurs in large specimens of Millepora, and, indeed, in many small 

 specimens too, leads to very great difficulties in the determination of 

 species which have been described on form as the principal character. 

 In Dr. Willey's collection there is a series of varieties of growth leading 

 from a massive lamellate form to a complicated branching and 

 anastomosing form. 



A careful study of these skeletons, then, points very definitely to 

 the conclusion that the general form of the corallum of Millepora should 

 be used, not as a primary, but as a very subsidiary character in the 

 description of species. 



The form assumed by the corallum must depend upon many circum- 

 stances connected with the exact spot on which it grows. If a Millepora 

 embryo happens to become fixed on a large piece of dead Coral, it will 

 form a large incrusting base, and such a base nearly always gives rise 

 to a lamellate form of growth ; if, on the other hand, the embryo settles 

 on a small stone or other object, lamellate growth is impossible, and the 

 corallum will be ramified. 



The growth of the corallum must also be influenced by the propinquity 



