Diplograpsus pristis with Reproductive Capsules. 319 



come into contact Avith each otlicr, just at tlic point of contact 

 and ajiparently within one of the capsules, are two minute 

 young graptolites, one lying across the other. Each consists 

 of a thin'' membrane, probably forming the 

 first partially developed pair of hydrothecas, ^o" ^■ 



a minute radicle, and a slender solid axis J^s. 



which is prolonged beyond the membrane. ^^^5^ 



They are similar in form and proportions; -y ^^_ ,. 

 but one is a little larger than the other. Ma<niVdiam8. 

 Its length, from the extreme 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 l-60th of 

 an inch wide, tapering towards the proximal end. The smaller 

 »]iecimen is l-30th of an inch in entire length, and l-80th 

 wide. If these young forms had not been in connexion with 

 a mature graptolite, they would have been considered to 

 belong to the genus Diplograpsus^ but it would have been im- 

 possible to refer them to any species. In their present posi- 

 tion I think we may without hesitation infer that they are the 

 young of the graptolite Avith 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 ad- 

 vanced state than either ; indeed on the same piece of shale 

 there are several young graptolites referable to the same spe- 

 cies, 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, hoAvever, Professor James Hall has detected diprio- 

 nidian graptolites with what he describes as " reproductive 

 sacs " or " ovarian vesicles." These are figured and described 

 in his ' Graptolites of the Quebec Group,' In Britain Dr. 

 Nicholson has described and figured, in the ' Geological ]\Iaga- 

 zine,' mono])rionidian grajrtolitcs Avith Avhat he has termed 

 ^' grapto-gonophores." If these should j^xoyq to be, as Dr. 

 Nicholson believes, the reproductive huds of graptolites, the 

 monoprionidian graptolite is reproduced in a totally different 

 manner to the diprionidian ; but I think Ave have as yet had 

 no sufficient evidence brought forAvard to proA^c that these 

 problematical bodies liave even any connexion Avith grapto- 

 lites. The discovery of this specimen throws no light upon 

 this mode of reproduction. It affords, on the other hand, a 

 decided confirmation of Hall's observations ; and as his vieAvs 

 have not been generally accepted, the specimen is perhaps of 

 more value than if it Avere unique. The reproductive sacs 

 figured by Hall are essentially similar to the gonotheca^ I have 



23* 



