448 Organization of Fossil Plants of the Coal Measures. [Mar. 27, 



previous memoir (" Phil. Trans." 1874, p. 56), I ventured to doubt the 

 correctness of Mr. Carruthers' conclusions, and expressed my conviction 

 that these objects resembled spores rather than protozoan skeletons. 

 Further study of their details of structure has only strengthened this 

 opinion which has also received the important support of Professors 

 Hgeckel and Strasburger, of Jena, both of whom have carefully studied 

 my collection of specimens. These objects are small spheres — the 

 sphere-wall of which is prolonged into a series of long radiating tubes 

 not unlike the muricated spines of a Cidaris. In their young state 

 each murication gives off a delicate thread or threads, which ramified 

 freely in an apparently mucilaginous or gelatinous, structureless, in- 

 vesting magma. In older specimens these threads developed into 

 branching and radiating cylindrical tubes which, like the primary ones, 

 had very thin walls. Within the outer sphere- wall, which consists of 

 bhe coalesced bases of these branching tubes, were at least two other 

 thin layers of membrane, and in several of the specimens the interior of 

 the capsule is filled with cells, exactly like those seen in the corre- 

 sponding cavities of Lycopodiaceous macrospores found in the Halifax 

 deposits from which the finest Traquairice have been obtained. These 

 objects differ considerably from all known reproductive structures ; 

 but I agree with Professor Hasekel in his very decided rejection of 

 them from the Radiolarian group of organisms, and with his conclusion 

 that they are vegetable and not animal structures. Professor Stras- 

 burger thinks it most probable that their affinities are with the 

 macrospores of the Khizocarpse. 



In my previous memoir I gave three very small figures of some 

 minute objects, which exactly resemble, in their minutest details, the 

 zygospores of some of the Desmidiaceae. Many additional examples 

 of these objects have been discovered, enabling me to throw further 

 light upon them. Their resemblance to these zygospores has been 

 made increasingly obvious, but I dare not venture to assign to them a 

 Desmidiaceous origin, since the most extended research, and the re- 

 sulting discovery of large numbers of these organisms, have yet failed 

 to bring to light the faintest trace of a true Desmid. Under these 

 circumstances I have assigned to several species of these organisms 

 the generic name of Zygosporites. 



The seed described in my last memoir but one, under the name of 

 Lagenostoma ovoides, always exhibited a thick carbonised testa, in 

 which no structure could be observed. I have now discovered that 

 the thick outer layer consisted of very hard cubical or slightly oblong 

 schlerenchymatous cells, whilst a thin and delicate inner membrane 

 was composed of small spiral prosenchymatous ones. 



An additional specimen of the woody axis of Dadoxylon exhibits the 

 paired divergent structures passing outwards to the back in the shape 

 of two large, radial prolongations of the cellular pith ; and which 



