313 
Bib Iw graphical Notices. 
colonies of minute transparent animals swimming in vessels of sea- 
water, during the months of February, March and April. Their general 
aspect very much resembled a flock of birds in distant flight, as re- 
presented by landscape painters. After being transferred to vessels 
free of other subjects, they continued several days in activity and 
then disappeared. I could not account either for their origin or their 
transience. They occurred only at rare intervals, and always iden- 
tically under the same form.” (p. 111.) 'I’hese very minute beings, 
for the expansion of an individual is only between one and two lines, 
were evidently allied to the Medusse “ both in configuration and in 
habits,” but they differed from the Medusse in the early date of their 
appearance. To distinguish them Sir John called the species Me- 
dusa bifida, and we have it minutely described and variously figured. 
Sir John was first led to remark that it was chiefly observed in ves- 
sels containing the Hydra tuba (p. 114) ; and subsequently, and as it 
were by accident, he discovered that the hydra was in fact their 
source ; and moreover that the hydra was identical with the Strobila 
of Sars ! The discovery is told in a most interesting manner, and 
with a truthfulness which there is ho gainsaying. 
We shall quote only a few of the many passages we have marked, 
previously observing that Hydra tuba in its strobila-form is some- 
thing like a fir-cone or a cylinder cut into several whorls, each whorl, 
when detached, becoming what is named the Medusa bifida. The 
strobila throws off these whorls in succession to the number of from 
ten to twenty, when the basis, as already stated, reassumes the form 
and habits of the hydra. 
“ First, a smooth fleshy bulb sustained a cylinder of about half its 
own diameter, indented by plain circles, which were soon converted 
to waving curvatures. A row of twenty or tv/enty-four tentacula 
crowned the summit of the cylinder, which row disappeared or was 
obliterated as the waving in its vicinity deepened, and the diameter 
of the cylinder there expanded, that is, towards the summit. Con- 
comitant on obliteration of the terminal row, a new circle of tenta- 
cula, at first few, but gradually augmenting, w^as emerging from 
around the bulb, while the struggles of Medusae, into which the 
waving strata were evolving, accomplished their liberation to swim 
unconstrained in the surrounding element.” (p. 121.) 
“ Certain facts admit of no dispute ; such as the existence of a 
vigorous hydra attached to a solid substance, with long flowing silky 
tentacula ; an alteration in the figure of the body, or the formation of 
an embryonic roll of Medusae on the disc ; the gradual maturity of 
each Medusa and its liberation from the roll ; the disappearance of 
the original tentacula of the hydra ; the emerging of a new circle 
of tentacula from a smooth fleshy bulb, sustaining the embryonic 
roll, as the former are obliterated, and as the Medusae approach ma- 
turity ; the evolution of thisfleshy bulb as a perfect hydra, along with 
their departure, which becomes the parent of progeny by gemma- 
tion, and its permanence as an independent animal.” (p. 122-3.) 
“ All the Medusae in the embryonic roll are separate and distinct 
animals. Each is in close application to that which is next below, 
if itself be uppermost, or lies between two if intermediate. The pro- 
Ann. ^ Mag. N. Hist. Scr. 2. Vol. i. 21 
