ROSACEUS, LINCK (COMATULA ROSACEA OE LAMARCK). 
535 
pseudembryo die at this stage, shortly after its death, a delicate film is sometimes 
separated from the surface of portions of the body, similar to the film which is 
observed under similar circumstances on the surface of Infusoria. I do not believe, 
however, that this film previously existed as a special membrane; but am rather 
inclined to think that it is produced after death by the coagulation of a layer of mucous 
excretion. Pyriform capsules of considerable size, about 0-03 millim. in diameter, 
are imbedded here and there in the superficial layer. These cells are of a pale yellow 
colour, full of a yellow fluid, which when the cell is crushed escapes as a round refrac- 
tive globule. The wide end of the capsule is superficial, the narrower extremity passes 
inwards and ends in a delicate thread-like process, which is lost in the substance of the 
sarcode. 
I have been able to detect no special wall to these capsules, the fluid of which seems 
simply to be enclosed in a pyriform space in the continuous sarcode : I regard these as 
reservoirs of oil. 
The peripheric layer is nearly free from granules ; but passing from without inwards, 
minute granules, compound granular masses, and endoplasts become more numerous; 
the sarcode at the same time apparently losing in consistency, till at length, towards 
the inner surface of the consistent perisomatic layer, it becomes densely granular, and 
no distinct line of demarcation can be detected between the sarcode which still retains 
a certain consistency, and the central semifluid protoplasm, in which the granules 
exhibit active molecular motion. The outer layer, when compressed and examined with 
a high power, exhibits between the endoplasts and oil-cells a very finely vacuolated 
structure. Minute spaces, somewhat like the lacunae of bone, filled with a clear liquid, 
are scattered through the sarcode ; and uniting these there is a system of exceedingly 
delicate tubules which may be compared to the canaliculi ; they are much less nume- 
rous, however, only about six or eight apparently radiating from each lacunar space. 
Even while under observation, the size of these spaces appears to vary, one or two which 
were prominent in one part of the field gradually contracting and becoming indistinct, 
while others previously scarcely visible seem to expand into view. I believe that this 
appearance is caused by the circulation of fluid through the system of vacuoles and 
vessels by movements depending upon the general contractility of the body-substance. 
Near the close of the free stage, when the embryo is beginning by its growth to distort 
the form of the pseudembryo, the integument of the wider anterior extremity of the 
pseudembryo immediately above the mouth of the embryo seems to become columnar in 
structure and opaque with closely packed long oil-cells, arranged vertically, and forming 
a kind of dome. In the earliest fixed stage this dome gradually splits up into the five 
oral lobes, each with its enclosed oral plate. 
The devlapment of the Skeleton . — To make the description of the development and 
relations of the parts of the calcareous skeleton of the pentacrinoid stage of Antedon 
intelligible, I shall in the first place describe very briefly the arrangement of the hard 
parts in the mature Antedon and in some nearly allied forms. I shall touch on this 
