76 THE VOYAGE OF H.M.S. CHALLENGER. 
Planule were not examined in the fresh condition, hence the ciliation of their 
surface, doubtless occurring, was not observed. In the most mature planula investi- 
eated, the endoderm consisted of pigmented cells, like those of the endoderm of the 
mature coral, but evidently in a condition of rapid increase, and of oil-globules of 
various sizes and fine granular matter, The endoderm mass did not show any trace 
of a central cavity, but appeared homogeneous and solid. The gonophore sacs seem 
to be permanent in Cryptohelia pudica, and the production of planule within them to 
be carried on as a continuous process. 
Growth by Budding.—In ordinary growth of the coral by budding, every part of the 
coral surface would appear capable of producing complete cyclo-systems, for in one 
specimen procured a new cyclo-system has been abnormally produced as a bud from 
the upper surface of the lid of an older cyclo-system. 
GENERAL REMARKS ON THE STRUCTURE OF THE STYLASTERIDZ. 
Summaries of the characteristics of the sub-order Hydrocorallinze and its subdivisions 
will be given in the sequel under the heading ‘ Classification.” A few further special 
points in the structure of the family of the Stylasteride require to be noted here. The 
Hydroid affinities of the Stylasteridee need no discussion; they are borne out by every 
item of structure. 
As in almost all Hydroids, the sexes are on distinct stocks, and these stocks, like 
those of Sertularians, have a tendency to grow in a flabellate form with alternate 
gemmation. In having the numbers of the tentacles borne by the gastrozooids regular 
in number in each species, possibly in each genus, the Stylasteride differ from the 
Milleporidee, in which the number is variable. The connection of an absence of the 
styles in the gastropores with a flask-shaped form of gastrozooid devoid of tentacles is 
remarkable. It occurs in apparently otherwise widely separated genera, Astylus and 
Pliobothrus. It is possible that the tentacles of the gastrozooids in all the genera 
would show traces at least of having knob-like or club-shaped ends were they examined 
in the fresh condition. 
The gonophore sacs within the ampulli, as containing several distinct gonophores, 
in several genera at least, seem entitled to the term “gonangia,” according to 
Allman’s terminology. It seems uncertain whether the central mass in Astylus, 
from which the sperm-developing lobules are budded off, is to be considered as a 
blastostyle or not ; no definite spadices were observed within these lobules. 
The radiate arrangement of the coenosareal canals around the sacs of the zooids, 
which is so remarkably developed in Sporadopora and Allopora, and traces of which 
appear in nearly all the genera, is very remarkable. It gives the soft structures of 
Allopora, at first sight, a still closer resemblance in arrangement to that occurring 
