232 REPORT ON THE STATE CABINET. 



are likewise numerous fibres of this kind traversing the sacs ; and these 

 sometimes remain attached to the original stipe after the other parts are 

 separated. In one example, we have conclusive evidence that they 

 are connected with the solid axis of the parent stipe. The gradations 

 of development in these sacs may be studied in figures 6-9, Plate i. 



In the specimen fig. 10 of the same Plate, the ordinary cellules are 

 removed, and the fibres are still seen joined to the axis, showing the 

 origin of the reproductive sacs. In most specimens bearing these sacs, 

 the cellules of the stipe are so obscure that the species cannot be deter- 

 mined ; but in fig. 9 we find them attached to a well-marked stipe of 

 G. wliitfieldi. 



This mode of reproduction in the Graptolites shows much analogy 

 with the hydroidea, and would indicate the sertularians as their nearest 

 analogues.* 



Upon the surface of the slate where these bodies occur, there are 

 numerous graptolitic germs, or young Graptolites of extremely minute 

 proportions, ranging from those where the first indications of their form 

 can be discovered, through successive stages of development till they 

 have assumed the determinate characters of the species. 



In several examples, these minute germs have been detected near to 

 and in contact with the reproductive sac ; and in one case, there is but 

 a hair's breadth between one of the fibres of the sac and one of the 

 oljlique processes at the base of the germ. It cannot be said that we 

 have detected the germ actually within the sac ; but the numerous young 

 individuals lying near them, and upon the surfaces of the same laminae, 

 offer very good arguments for supposing that they have been thus 

 derived. 



The earliest defined form which we observe in the young Graptolites 

 consists of the initial point or radicle ; a diverging process of similar 

 character on each side, but not quite opposite ; a longitudinal axis of 

 greater or less extent; and a sac-like covering, or a thin pellicle of grap- 

 tolitic test, which has scarcely assumed the form of cellules, but which 



* In the recent Seetularia and Campanularia we find ovarian vesicles, in which a numher 

 of ovules may be enclosed in a cominon envelope. These vessicles are developed along the side 

 of a stipe or branch, and the ovules are often arranged along a central axis, each one communi- 

 cating with the common axis of the zoophyte. ( Jas. J. Lister, Philosophical Transactions, 1834, 

 pp. 365-388, pi. ix. Cited also by Dana, " Structure and Cla^nijicatiun of Zoophytes." 



Prof. M'CoT has stated (^British Palaozoic fossils, p. 4) that he has found near the base of 

 the cellules of Graptolites, a transverse partition or diaphragm, similar to what may be observed 

 in some sertularians, and which he regards as proving similar relations ; but I have not discovered 

 in any American specimens, evidence of such cell-diaphragms. 



