No. 186.] 



55 



substance of the sac gradually disappears, apparently by decomposi- 

 tion, leaving the slender fibre still attached for some time to the 

 axil of the serrature. 



These buds or vesicles do not appear at every serrature, but only 

 on every third or fourth, and are apparently opposite each other on 

 the two sides of the rachis, but in reality alternating as do the ser- 

 ratures. Associated with these specimens, and apparently resulting 

 from these vesicles, are numerous young graptolites. But although 

 these young or embryonic forms of graptolites occur in such great 

 numbers, it cannot yet be said that any specimens have been seen 

 within the sac, or attached to the parent stipe*. 



The following figures will render more clear the preceding ob- 

 servations, and illustrate in some degree the forms described. 



rig. 1. A fragment of the stipe, showing the earlier development of these bnds or 

 vesicles. 



Fig. 2. A fragment where these biids are farther developed, and the npper ones less 

 expanded than those below. 



Fig. 3. A longer stipe preserving numerous expanded vesicles in a farther developed 

 condition; the most of them being broken, and some of them partially de- 

 composed or absorbed, while they preserve very distinctly the delicate hair- 

 like fibre before mentioned. 



* The first discovery of a specimen of this character is due to Mr. Whitfield, some 

 three years since; and subseqnentlj^ I have been indebted to Mr. J. B.Ellis, and to 

 Mr. G. W. Taylor, for other specimens of the same, as well as for other forms; while 

 I owe to Mr. Henry Canfield the possession of the very fine specimen of G. gracilis 

 figured on page 58. The discovery of the young graptolites has been of later date, and 

 they hare recently been observed in large numbers. 



