8 
SECOND YARKAND MISSION. 
There are no diaphragms in the tubes. In some types a part of the tube-wall is 
so homogeneous as to render the possibility of the former existence of a membrane well 
worthy of consideration; hut in the majority of instances, the construction of the wall is 
evidently of close and semi-spiculate granules and of shapeless granules, and was 
probably not quite impervious. The tubes are tilled with calcite. They are often perfectly 
transparent, and at other times impervious to light. Under high powers the structural 
element of the tube is shown to he mainly spiculo-granular and molecular; the grains 
usually being xo^o^ t soo o inch, or less in breadth. But in some instances there are elongate 
pieces with spiny processes on them, all being however excessively small. The structure of 
the tube-wall was organic in its origin, and not the result of simple adhesion of foreign 
or arenaceous particles. 
The question whether there is an intertuhular coenenchyma of fibres, or a reticulate skeleton, 
which supports the tubes, separates them, and allows the symmetry and ornamentation 
of the surface to he kept up, is by no means readily answered. The examination of the 
forms of Syringosphceridce, with the radial series of tubes separated by much tube reticula¬ 
tion, leaves this question not satisfactorily solved. The fossilization is by calcite, and the 
cleavage planes, commencing cleavage planes, irregular crystals, and cracks show dark lines 
by transmitted light, which in many instances resemble sponge structure, and even in one 
instance a hexactinellid spicule was .suggested to the eye. Polarized light, with or without the 
selenite plate, resolves these markings into the limiting lines of different crystals, and, although 
one or two evidently extraneous organic bodies have been seen amongst the tubes, no continu¬ 
ous or partial interskeleton can be determined to exist now. In the centre of the masses, 
the confusion of tube radiations, cleavage planes, and the presence of some foreign body, which 
formed in some instances the nucleus, or rather the starting point of the SyringosphmridcB, 
renders it impossible to decide dogmatically whether there is a coenenchyma or not. On the 
other hand, in those forms where the tubes are close, even in the interradial series, the 
absence of coenenchyma is evident enough. Under correction, and relying on the specimens 
examined, I do not think that there ever was a structure in them external to the tubes and 
which supported and separated them after the manner of a coenenchyma. 
The position of these spherical and spheroidal masses of radiating and interradiating 
tubes in the classificatory scale must be low. The minute size of the tubes, their bifurcat¬ 
ing so frequently, and inosculating, and giving off others from small offshoots, and the struc¬ 
ture of the wall, do not render the SyringospJiceridcB polyzoan in their nature. The analogy 
with the tubular or more or less globular masses of Fascicularia found in the English Crag 
is of the slightest in degree. It is tempting to theorize, so as to place a Gastrozooid in each 
pore, supplying it by the radial tubulation, and to decide that the tubes of the interradial series 
opening at the surface were those of Daclylozooids, the whole being a by droid. But the 
absence of pores in some forms, the evidence that there are places where growth is not pro¬ 
ceeding in others, and the deficiency of surrounding open tube mouths in most, prevents 
this idea from having any value. There are moreover no tabulae in the tubes. 
That these great and small spherical and spheroidal masses are corals is, of course, out 
of the question, and the evidence of their sponge nature is small. 
Had there been a coenenchyma between the tubes, the bodies would have resembled 
foraminifera, with gigantic canal systems, but its absence and the peculiar nature of the tube- 
wall remove these forms from that polymorphic group. The absence of labyrinthic spaces, 
