206 JOHN HOPKINSON ON DIPLOGRAPSUS PRISTIS. 



or crumpled, or traversed by fibres which extend for some distance, 

 into the body of the polypary. Some are much twisted and bent 

 about, occasionally overlapping each other. Between two which 

 thus overla]?, or perhaps only come into contact with each other, 

 just at the point of contact and apparently within one of the cap- 

 sules, are two minute young graptolites, one lying across the other. 

 Each consists of a thin membrane, probably 

 forming the first partially developed pair of s ' 



hydrotheca?, a minute radicle, and a slender 

 s olid axis, which is prolonged beyond the 

 membrane. They are similar in form and 



proportions ; but one is a little larger than 



., ., ti t ,1 n ,i Young graptolites. 



the other. Its length, from the extreme Magu. 6 diams. 



point of the radicle to the distal end of the 



axis, is l-20th of an inch. The membrane itself is about half this 

 length, and 1-G0th of an inch wide, tapering towards the proximal 

 end. The smaller specimen is 1-S0th of an inch in entire length 

 and l-80th wide. If these young forms had not been in con- 

 nexion with a mature graptolite they would have been considered 

 to belong to the genus Diplograpsus, but it would have been impos- 

 sible to refer them to any species. In their present position I 

 think we may without hesitation infer that they are the young of 

 the graptolite with which they are associated. That they have not 

 yet entered upon independent existence we cannot conclude ; for 

 they are in different stages of growth, and young graptolites are 

 frequently met with in a less advanced state than either ; indeed 

 on the same piece of shale there are several young graptolites 

 referable to the same species, and no more developed, some even 

 less so. 



This is the only graptolite with undoubted reproductive organs 

 yet known to have been found in Britain. In America, however, 

 Professor James Hall has detected 'diprionidian graptolites with 

 what he describes as " reproductive sacs" or " ovarian vescicles." 

 These are figured and described in his " Graptolites of the Quebec 

 Group." In Britain Dr. Nicholson has described and figured, in 

 the " Geological Magazine," monoprionidian graptolites with what 

 he has termed " grapto-gonophores." If these should prove to be, 

 as Dr. Nicholson believes, the reproductive buds of graptolites, the 

 monoprionidian graptolite is reproduced in a totally different manner 

 to the diprionidian ; but I think we have as yet had no sufficient 



