TRANSACTIONS OF SECTION D, Véa 
species, the pollen is sound.’ A little further on Darwin says ‘these facts indicate 
that there is some relation between the state of the reproductive organs and a 
tendency to variability; but we must not conclude that the relation is strict.’ 
Finally he sums up the matter in these words: ‘On the whole, it is probable that 
any cause affecting the organs of reproduction would likewise aflect their product— 
that is, the offspring thus generated.’ 
FRIDAY, SEPTEMBER 15. 
The following Papers were read :— 
1, Astrosclera Willeyana, the type of a new family of Recent Sponges. 
By J. J. Lister, IA., £.Z.8., Demonstrator of Comparative Anatomy 
in the University of Cambridge. 
In the collections brought home by Dr. Willey from the Western Pacific were 
four specimens of a peculiar hard white organism which he found growing on dead 
coral at a depth of 30 fathoms, in Sandal Bay, Lifu, Loyalty Islands. These he 
has placed in my hands for examination. The specimens are cylindrical in shape, 
and measure about 10 mm. in height and 5 mm. in breadth. The base is slightly 
spreading, and the upper surface gently convex. 
Skeleton.—The skeleton is formed of solid polyhedral elements, which are 
composed of crystalline fibres radiating from a central point. They are united 
into a mass so rigid that to obtain sections of it slices were cut with a fret-saw, 
and, after embedding in copal by von Koch’s method, were ground down thin on a 
hone. The mineral constituent of the skeleton is carbonate of lime in the form— 
as the specific gravity shows—of aragonite. The skeleton is permeated by canals 
which open only on the upper surface. There is no large central space to which 
the canals are tributary. Many are approximately parallel with the axis, and they 
communicate very freely by branch canals, which run from one to another, dividing 
and anastomising (see fig. on p. 776). 
The sides are smooth and imperforate, while the curved upper surface is closely 
pitted by the openings of the canal system. In one specimen the upper surface is 
traversed by grooves, which radiate, with an approavh to symmetry, from one 
point. These are apparently radially directed canals of the skeleton in course of 
formation. There is no indication that the central point is occupied by a canal 
larger than the others, whose openings are scattered over the surface. 
The ridges of the skeleton between the openings are produced into irregular 
crests and points formed of skeletal elements, which are more and more loosely 
connected with one another as the surface is approached. 
The gelatinous layer which invests the upper surface is crowded with young 
growing skeletal elements, the small ones free and spherical, the larger packed 
together like hailstones, and assuming the polyhedral form. 
Origin of the Skeletal Elements.—The spherules take their origin in single 
cells of the jelly, near the upper surface. In the early stages of growth the 
granular nucleated cell body is seen as a thin investing layer surrounding the 
spherule, which’is from the first composed of radiately arranged crystalline fibres. 
As the spherule increases in size it takes up its position as an element of the 
fixed skeleton, and in the course of their growth the angular spaces between 
adjacent skeletal elements are completely filled in to the exclusion of the soft 
parts. The elements thus lose their spherical shape and become polyhedral. The 
external surface of a spherule in contact with a layer of soft tissue is often beset 
with radiating points, and resembles a portion of a spheraster of a siliceous sponge. 
After decalcification a more or less abundant organic basis of the skeleton is left ; 
the central parts of the spherules take a deeper stain, and are thus marked off from. 
the peripheral portions, 
