GRAPTOLITES. 23 
the celluliferous portion of the stipe, and, in one species, uniting in a 
funicle, and forming part of a compound form. In another species, the 
simple stipes present similar features, showing at one extremity the 
duplicate character of the axis. 
In Phyllograptus, the central axis is apparently composed of four 
slender flat lamin ; but we have had no means of examining this part 
of the body in a satisfactory manner. 
2. The Common Canal.—lIn all graptolites with a single series of 
cellules, there is, between the bases of these cellules proper and the solid 
axis on the back of the stipe, a continuous sub-cylindrical space or canal, 
which has been occupied by the body of the polyp, from which the buds, 
with their calycles forming the cellules, take their origin, and are thrown off 
at regular intervals. : 
All the specimens which I have examined confirm this view; and in 
some of the species where the extremities are apparently entire, we observe 
the incipient development of the young cell from the common body. In 
those specimens filled or partially filled with the substance of the surround- 
ing rock, this canal is easily distinguished ; while in compressed specimens 
there is always a flattened space between the bases of the cell-partitions 
and the solid axis. 
Tn those graptolites with two ranges of cellules, we have apparently a 
duplication of those with the single series, the two solid axes being jomed 
together, leaving a common canal or body on each side at the base of 
each series of cellules. If however the common body were thus divided, 
it would be by the solid axis becoming a flattened plate. This appears to 
be true of some species (as for example, plate A, fig. 10), while in others 
there is only a simple filiform axis visible. In this case, of course, there 
is not an entire division in the common canal after the manner of the 
other species. ‘This will appear farther on, under the illustrations of the 
structure of these bodies. 
In Retiolites, the common body occupies the central portion of the stipe, 
giving origin to a series of buds on each side, while it is not divided by a 
central axis. 
In some species the common body seems likewise to have more extensive 
functions ; for in such forms as G. divergens and G. gracilis, there is a 
long slender rachis, or tubular body, destitute of cellules except at its two 
extremities, and apparently consisting of a solid axis and a common canal, 
from which originate, at regular intervals, simple small stipes with solid 
axis, common canal, and cellules. 
This appears to be one step farther in our knowledge of the origin or 
mode of development ; but it shows that a stipe or main axis may produce 
in one part celluliferous stipes, and in its extremities develop only cellules, 
as we see in the continuation of the main axis of G. gracilis and 
