82 Mr. G. E. Vine on ^jpecies of 



3. Ascodictyon radiciforme^ Vine. 

 = Ascodicf 1/071 radians?, Vine, Quart. Journ. Geol. Soc. Nov. 1881, 



p. 619. 

 = Ascodictyon radiciforine, Vine, Q. J. Geol. Soc. Feb. 1882, p. 53. 



When I wrote the details already given in the papers re- 

 ferred to above I did not possess the fine suite of specimens 

 which has enabled me to extend my remarks on the origin, 

 growth, and apparently final (?) development of this peculiar 

 group of organisms, found as yet only adherent to other 

 organisms in the Wenlock shales. 



In speaking oi A.filiforme^ I incidentally referred to a single 

 form apparently related to the S])ecies, but which I said it 

 would be best to keep separate. I have now to consider the 

 relationship of that form, but which, not being the earliest in 

 the development of the species, I will defer till later on. 



In fig. III. 5 I have sketched the fragment of acrinoid stem, 

 magnified about 2 diameters, on which one of the finest of my 

 colonies of the earliest stages of this species [A. radiciforme) 

 is attached. I do not, however, found the whole of the evi- 

 dence which I am about to bring forward on a single specimen. 

 I have corrected both the positive and the negative evidence 

 by appeals to between sixty and seventy other specimens ; but 

 as this one affords me evidence of continuous growth, I have 

 built up my description mainly on it. And here I must be 

 allowed to say that, contrary to my general plan in drawing, 

 the whole of my sketches are drawn by the eye, and not by the 

 aid of the camera lucida j but every figure is a faithful delinea- 

 tion of the original. 



In fig. III. 1, 2, and 3 I have drawn a fibre which is conti- 

 nuous on the fragment of crinoid stem already referred to. At 

 2, a and a', we have two nuclei, either of which may be 

 referred to as the originating nucleus of the colony ; but it 

 will be best to speak of them separately. In fig. III. 2, a, a kind 

 of false stellate cluster is formed ; but this I regard as only an 

 offshoot ; the true nucleus is at a', and at this the central part 

 only. It appears to me that the central nucleus originates by 

 the combination of minute spores, which up to the present 

 have escaped my observation ; but immediately after the 

 combination, delicate prolongations of the central mass or 

 radii are sent off which do not in every case produce fibrous 

 threads. At a one of these minute combinations is formed, 

 but only one of the rays is apparently developmental *. 



* It will be understood by the palaeontologist that in restricting myself 

 thus I only take the evidence presented to me. I have not the least 

 doubt but that -what I sa}^ of one might be said of all the rays ; but I 

 have only the one evidence to rely upon — the positive. 



