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 ; but 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 filled 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 be mainly spiculo- granular and molecular; the grains 

 usually being yowo, 15000 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 intertubular coenenchyma of fibres,or a reticulate skeleton, 

 which supports the tubes, separates them, and allows the symmetry and ornamentation 

 of the surface to be 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 Syringosphceridce, 

 renders it impossible to decide dogmatically whether there is a ccenenchyma 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 Syringosphceridce 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 tabulation, and to decide that the tubes of the interradial series 

 opening at the surface were those of Daclylozooids, the whole being a hydroid. 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 ccenenchyma 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, 



