Zoological Position of the Graptolitide. 59 
the stipe of Graptolites Sedqwickti. 'These bodies differ from 
those noticed by Hall in being free in the later stages of their 
growth, instead of remaining permanently attached. They 
are oval or bell-shaped, cited with a mucro or spine at one 
extremity, and a a by a strong filiform border, which 
ultimately ruptures. In many instances these bodies may be 
seen, when small, to be attached to the cellules of Graptolites — 
Sedgwickit; and they appear sometimes to spring from the 
common canal, though this is rare and is perhaps accidental. 
That these bodies are connected in some way with repro- 
duction appears to me to be beyond doubt. ‘They resemble 
the “ gonophores”’ of the recent Hydrozoa in being external 
processes, In some cases permanently attached, in others ulti- 
mately detached ; the likeness in form is also striking. They 
differ, however, in possessing a corneous envelope, so that, 
when detached, they were either simple free-floating organisms, 
or, if they possessed any independent locomotive power of 
their own, this must have been obtained by means of cilia or 
by some soft apparatus which would leave no traces of its 
existence. It is probable that the capsules did not contain 
the germs of Graptolites as we now find them in a fossil con- 
dition, as thought by Hall, but that their contents were the 
ova in their earliest stages. The ova would probably be libe- 
rated, on the dehiscence of the capsule, as minute ciliated free- 
swimming organisms, which subsequently and as a later de- 
velopment acquired acorneousenvelope. With regard to other 
species of Graptolites, it may be looked upon as probable that 
the gonophores, if corneous, were attached to the sides of the 
polypites or to “ gonoblastidia,” whilst in other species, 
again, the gonophores were probably without any corneous 
test; so that the great majority of species will perhaps never 
be found in conjunction with ovarian capsules, either free or 
- in connexion with the parent stipe. Judging, however, from 
_ analogy, there seem to be good grounds for the belief that the 
_ reproductive process in all the Graptolitide was in all essential 
_ points identical with that of the Hydrozoa. 
_ Mode of Existence.— As to the mode of existence of 
the Graptolitide, there can be no question that by far the 
_ greater number were free-floating or free-swimming organisms. 
& some species of Dichograpsus, Tetragrapsus, and Diplo- 
_ grapsus, there are the remains of a body (the “ disk’’) which, 
as I have aleady said, probably acted as a float, and finds its 
__ best homologue in the “ pneumatocyst”’ of the Physophoride. 
Other genera, as Grraptolites, Phyllograpsus, Pleurograpsus, 
Retiolites, &c., were very possibly provided with “ necto- 
calyces”’ or “ swimming-belis;”’ but these, of course, could 
9 
