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a footing, and you will understand how the myriads of medusae 
cover the surface of the sea beneath the summer sun, and make 
it glow through the summer night. 
Alexander Agassiz tells us that one of the budding kinds, ap- 
propriately named “fulgurans ” (“ light-flasher ”), is sometimes 
so abundant off the American coasts, that the sea, when dis- 
turbed, is brilliantly lighted by its blue phosphorescence. And 
of another species he says that he had often found the whole 
surface of the water, for several miles in the Grulf of Georgia, 
thickly covered with it. 
To return to our budding, the case which we have been 
considering is simple enough, and in harmony with the whole 
course of hydroid history. But the facts now to be noticed are 
anomalous and difficult to interpret. A medusa has been ob- 
served to bud off young within the cavity of the stomach, and 
these, when developed, have taken on a form which is totally 
unlike the parent ; which belongs, indeed, to the medusa of 
another, and very different Family. In other words, two distinct 
types of medusa originate one from the other and form parts 
of one and the same life-series. These observations, if correct, 
are certainly startling ; we are scarcely, I think, in a position 
at present to determine their true significance. It would be 
satisfactory to have them confirmed, eminent as the authorities 
are to whom we owe them, and to know more than we now do 
both of the earliest and of the later stages of the remarkable 
life-history. If it should prove to be a fact that one hydroid 
medusa may originate another by gemmation of an entirely 
different generic type, we must materially enlarge our con- 
ception of the polymorphism of the zoophyte, and modify our 
systematic views. So remarkable a divergence from the direct 
line of development would open the way for much curious 
speculation. The observations of Haeckel and others on this 
point are deeply interesting, and indicate to the zoologist a 
most fruitful field of research. 
I have spoken of the swimming-bell as the characteristic 
feature of the medusa ; but there exists a small group of forms 
in which it is suppressed, and its place is filled by a totally 
different locomotive organ. In Clavatella (Plate LXXXVIII., 
fig. 8) the contractile float is wanting, and we have an ambulatory 
medusa, which moves about leisurely on suctorial feet, or climbs 
by their aid among the algss. In this remarkable creature, the 
general form of the medusa is preserved, the radiating canals 
are traceable in the walls of the hemispherical body, the ocelli are 
conspicuous at the base of the tentacles, the portion of the 
central sac bearing the mouth hangs below the disc; but the 
beautiful contractile float is missing. In its absence, however, 
a new compensative element makes its appearance ; the tentacle 
