STUDY OF THE GBAPTOLITES. 223 



stipe or branch, and of course a division of the solid axis and common 

 body. 



In Retiograptus, some specimens show the cell-divisions reaching 

 nearly to the axis, leaving room on each side for a narrow common body 

 or canal; while in a species from the Utica slate, which presents one 

 side of an entire frond, the cell-divisions of the exterior side all reach 

 to the axis, leaving the common body on the other side.* In a species 

 from Norman's Kill, near Albany, there are three parallel ranges of 

 reticulations, with apparently two filiform solid axes, forming the 

 divisions between the three meshes. This structure probably occupies 

 one side of the stipe, while the common body may occupy the other 

 side. 



In Phyllograptus, the cell-partitions reach very far towards the 

 centre, and the space left for the common canal is very small. We infer 

 from the better preserved specimens, that there is a slender common 

 canal at the base of each range of cellules. These several canals may 

 or may not communicate with each other.t 



3. THE CALXCLES OB CELLULES. 



Since a large proportion of the specimens of Graptolites which come 

 under our observation for the purposes of study or otherwise, are frag- 

 mentary, it becomes of much importance to know the general characters 

 of form and mode of development of the cellules. 



In the preceding section it has been shown that the cellules, or the 

 inhabitants of these cellules, are not independent, but all have their 

 origin in a common body which fills the longitudinal canal, and that 

 they remain in • constant connection with the same throughout their 

 existence. 



The calycle or cellule is formed by budding from one side of the com- 

 mon body, not unlike many of the Sertularians, except that the cellules 

 are generally close together at their origin. They are usually more or 

 less oblique to the direction of the axis, as is clearly indicated by the 

 cell -partitions; and the degree of obliquity often indicates specific 

 distinction. The cellules are for the most part contiguous at their origin, 



* The expression here used is from an idea that the original form of the frond is funnel-shaped ; 

 and the inner side, upon which the common canal would he visible, now lies against the stone. 



t 5Ir. Cakrdthers, in his recent paper on Graptolites, assumes that Phtllograptus has no 

 common canal or common body; but I do not know on what evidence this view is based. There 

 seems to me a narrow semicircular space at the base of each cellule ; and these, communicating 

 longitudinally, form the common canal which is occupied by a continuous body or canosarc. 



