232 Report of the State Geologist. 



It is true it does not show the conical plug or disc on top, but 

 neither is this always present in the recent Sertularians. 



1 have not been able to find how the gonangia opened. The 

 clusters of siculse which appear on young colonies (PI. Ill, figs. 

 15, 16, IT, "zO) lead to the supposition (as we shall see more 

 extensively later) that the basal siculse remained attached to the 

 colony, while the more distal ones were detached. This, in its 

 turn, would suggest an opening at the top of the gonangium. 



The gonangia of Diplograptus resemble in all more important 

 features, i. e., the shape of the gonangium, the substance of the 

 periderm, the possession of a blastostyle, its shape and position, 

 the gonangia of the Sertularians so closely that we must regard 

 not only the possession of these organs but also their structure as 

 arguments for the hydrozoan nature of the Graptolites. 



Gonangia were described as long ago as 1859, when J. Hall pub- 

 lished his fundamental researches on the Graptolites of the State 

 of E"ew York. (Geol of the State of N. Y. Pal., vol. III.) The 

 author describes stipes of Diplograptus Whitfieldi, Hall, bearing 

 appendages, which are regularly or alternately arranged in two 

 opposite rows on the stipe, the thecse being suppressed or 

 the vesicles proceeding from their axils. The appendages appear 

 at first as buds of oval shape, which become later on, apparently 

 by dehiscence or decomposition and absorption, irregulary trian- 

 gular. They have scarcely • any substance except a filiform 

 border. Although there are upon the surface of the slate, where 

 these bodies occur, numerous siculae, no germ could be found 

 within a sac, and only one apparently attached to such an append- 

 age. Hall compared them with the gonangia of the Sertulariae 

 and Campanulari^. 



Other appendages have been found and described in England 

 by H. A. Nicholson.^ They were found in the Graptolite rocks 

 of Dumfriesshire, attached, in some instances, to the stipes of Gr. 

 Sedgwicki, ISTich. They differ from those noticed by Hall in 

 being free in the later stages of their growth. They are 

 described as *^ oval or bell-shaped, provided with a mucro or spire 

 at one extremity and surrounded by a strong filiform border, 

 which ultimately ruptures." Nicholson found these bodies, which 



* Cf. Ann. & Magaz. of Nat. Hist., 1868, vol. I, p. 55. Nicholson gave a brief description before this 

 publication in a paper which I have not been able to obtain. 



