320 On Diplograpsus pristis with Ueiiroductive Gajpsules. 



here dcscriljcd ; upon the surface of the shale on which they 

 occur there are numerous young graptolites in various stages 

 of growth ; and in one specimen figured, " in connexion with 

 one of the sacs there are two minute germs, one of them lying 

 beneatli the sac, and the other just beyond its outer margin 

 and barely separated from its fibres "*. 



The presence of these reproductive capsules throws some 

 light upon the affinities of gra])tolites. It confirms the evi- 

 dence which their internal structure has already furiiished, of 

 their near alliance with the Ilydroida. The rcju'cductive 

 organs of the Actinozoa and of the Polyzoa being internal, 

 graptolites cannot, as some think, belong to either of these 

 classes. In the Hydrozoa they are external ; and in some of 

 the Ilydroida (the only subclass of the Hydrozoa with wliich 

 graptolites, having a chitinous polypary, can be compared) 

 there are reproductive capsules essentially similar to those of 

 the gra]5tolite, although in no single instance entirely agree- 

 ing with them. We have no single recent Hydroid with 

 reproductive organs enclosed in chitinous capsules which are 

 destitute of any distinct orifice, are bounded by a marginal 

 fibre, or com])osed of two membranes united at their edges, 

 and at the same time bud from the periderm without inter- 

 fering with the continuity of the hydrotheca? ; but these ap- 

 pearances are all presented by one or other of the Hydroid 

 zoophytes. In Sertulariaj Di'pliasia^ &c., the gonothecas bud 

 from the periderm in the same manner as in the graptolite; 

 in several genera they are ribbed or thickened at their edges, 

 and in one genus, if not in more, they have no definite distal 

 orifice. In Af/laojiheniaj I have been kindly informed by the 

 Kev. Thomas Hincks, the gonotheca " is oval in form, without 

 orifice, and bounded by a very thin and delicate chitinous 

 wall." 



I need only add that graptolites, having, as is here shown, 

 true gonothecfe as well as hydrothecfe, are most nearly and 

 intimately allied to^ that order of the Hydroid Coelenterata 

 known as the Thecaphora or Hertularina. 



The specimen Avhich has formed the subject of these remarks 

 was collected by the Geological Survey of Scotland, at Lead- 

 hills, Lanarkshire, along with a series of fossils which parallel 

 the rocks of tliis locality with those of Moffat, Dumfriessliire, 

 or with the Llandeilo Flags of Wales. 



* Grapt. (Quebec fJroup, expl. pi. b. fig. 8. 



