14 THE VOYAGE OF H.M.S. CHALLENGER. 
the surface of the coenosteum in well-marked and separated systems, and in this respect 
is more closely allied to Millepora plicata, Millepora foliata, and Millepora ehrenbergi, 
as described by MM. Milne-Edwards and Haime. 
In the fresh condition the growing tips of the lobes of the coral are of a bright 
gamboge-yellow colour, which shades off into a yellowish-brown on the sides and bases 
of the lobes. The expanded zooids have the appearance of a close-set pearly white 
down upon the surface of the coenosteum. 
The zooids seem to be somewhat capricious in the matter of expansion. I made one 
attempt to obtain them expanded, in which I carefully cut off masses of the coral by 
means of a chisel and transferred these to a glass vessel without lifting them above the 
surface of the water. The zooids did not expand. Mr Murray succeeded on both 
occasions on which he collected specimens, although he exposed his to the air for a 
moment on transferring them to a vessel. Dana, Pourtales, and others speak of the 
peculiar difficulties attending the observation of the animals of Millepora. The ecenosteum 
is so hard that it is almost impossible to break off a small flake without damaging 
the soft structures to such an extent that the animals fail to expand. The animals, 
as expanded on larger masses of the ccenosteum, can only be examined with very low 
powers of the microscope, which, on account of the very small size of the animals, are 
unable to show sufficient details in their structure. A momentary view of one dactylo- 
zooid was, however, obtained under Hartnack’s objective No. 4, eyepiece No. 3. I 
obtained the view of the expanded zooids only on the morning on which H.M.S. 
Challenger was steaming out of Papiete Harbour. The animals remained expanded 
about two hours, but the motion of the ship interfered considerably with the investiga- 
tion of them. 
LITERATURE OF THE SUBJECT. 
M. Milne-Edwards (Hist. Nat. des Coralliaires, Paris, 1860, tom. 1. p. 224) formed 
the family Milleporidee to include a series of genera, amongst which Millepora and 
feliopora are the only recent ones, whilst he classed the Pocilloporinee as a sub-family 
of the Favositide, together with the Milleporide and Seriatoporidee, under his section of 
the Madreporaria Tabulata. The section was characterised by him as having the corallum 
composed essentially of a much developed mural system, with the visceral chambers 
divided into a series of stories by complete diaphragms or transverse floors, the septal 
arrangements being rudimentary or represented by trabeculee, which have a greater or less 
extension in the intertabulate spaces. In his description of the Mulleporidee (/. c.) M. 
Milne-Edwards referred to Professor Agassiz’s then recent paper, entitled ‘Les Animaux des 
Millépores sont des Acaléphes Hydroides et non des Polypes” (Bibl. Univ. de Genéve, 
Arch. des Sci., Mai 1859, tom. v. p. 80), to the following effect :—‘ At the moment of 
