Nicholson — On Graptolites. 259 



curious phenomenon, which is of importance if duly confirmed by 

 further researches. In a specimen kindly lent me by Mr. D. J. 

 Brown of Edinbui-gh, the stipe is studded with small rounded 

 tubercles, about as large as the head of an ordinary pin, and ap- 

 parently springing from the common canal on either side (Plate XI. 

 Fig. 5). As nothing of this kind normally exists in any Graptolite, 

 I am inclined to believe that we have here an instance of ovarian 

 vesicles in their young condition, which may either remain per- 

 manently attached, or may possibly become fi'ee at a later stage. If 

 this conjecture should prove to be correct (and it is difficult to see to 

 what else these bodies could be referred), it will form another, and 

 a strong, confirmation of the view that the Graptolites should be 

 classed among the Hydrazoa. I am, however, bound to admit that 

 this is the only instance in which I have succeeded in detecting these 

 bodies, so as to be able to speak with certainty as to their existence. 

 I certainly think I have seen similar tubercles in other specimens of 

 P. linearis, and also in Diplograpsus hicornis, Hall ; but the difficulties 

 of observation are very great, and I should not like to make any 

 positive assertion on this point. 



This leads me to make a few remarks upon the bodies recently 

 described by myself, as being probably the " gonophores," or ovarian 

 vesicles, of Graptolites (Geol. Mag., VoL III. p. 488, Plate XVII), 

 concerning which I have been fortunate enough to obtain further 

 and more conclusive evidence, in a series of well-preserved specimens. 

 When perfect, and compressed laterally, these bodies are oval, bell- 

 shaped, pyriform, or rounded, provided with a mucro at one extremity 

 (the proximal?), and surrounded entirely by a filiform border re- 

 sembling in texture the axis of a Graptolite (Plate XI. Fig. 8). 

 When more advanced in growth the capsule apparently ruptures, 

 and the distal margin then becomes ill-defined and irregular, owing 

 to the destruction and absence of the border above mentioned (Plate 

 XI. Fig. 9). When compressed from above downwards, the mucro 

 is to be found somewhere within the circumference, as an elevated 

 point surrounded by several concentric, circular, or elliptical rings 

 (Plate XI. Figs. 10-11). The resemblance in these cases to orbicular 

 Brachiopods is purely mimetic and illusory, and could not deceive 

 anyone who had examined a large series of specimens. They are at 

 once distinguished by their often large size, by the irregularity of 

 the concentric rings, by the variable position of the mucro — which 

 is sometimes centric, sometimes eccentric — and by their total want 

 of any persistent figure, outline, or striation ; while their texture is 

 graptolitic, and entirely different from that of any Brachiopod, such 

 as the Siphonotreta micula. In the case of that variety — if variety 

 it be — of Graptolites SedgivicJcii, described by Professor Harkness^ 

 under the name of Bastrites triangulatus, I believe I have now made 

 out with certainty, that these capsules are reproductive in function, 

 having obtained them in attachment in such numbers, and under 

 such circumstances as seems to preclude the possibility of accident. 

 They seem, however, to become detached before they attain their 

 1 Quart. Joiirn. Geol. Soc, Vol. vii. 



