“ MEDUSA DUODECILIA.” 69 
“As in some other Medusa, the ciliary or tentacular organs resemble knotted cords. 
Each pair originate from a prominent knob or button on the margin of the cavity in the 
under part; and a black speck, like an eye, is conspicuous at the root of each tentaculum : 
there are, therefore, eight in all. The transparent convex surface of the animal is crossed by 
two darker lines at right angles, as if dividing it into quarters, and terminating in the four 
buttons or knobs on the margin. 
“ The opacity of this creature, during its earlier stages, is not such as entirely to intercept 
the light, though its transparence refines in proportion to the evolution of its organization. 
Thus, the cross lines running from what was conjectured an orifice are discovered to be four 
vessels, wherein a fluid carries a number of black particles down to the marginal knobs below. 
It rather appears also, though I could not satisfy myself of the fact, that the current may pass 
in another course around the margin. 
“We should be much deluded, as well as our fellows, in believing that sufficient oppor- 
tunities are afforded for similar observations by the Medusa free of the zoophyte, and swimming 
at large. On the contrary, they can be effected only while immaturity yet restrains the 
animal to its pristine site; and where, during progressive evolution, the microscopical focus 
can be accurately adjusted for distinct vision. The motion of so restless a being, when 
liberated, renders correct observation incompatible with that condition. 
“One of the pyrula seemed to be united to a hydra, just at the orifice of the twig from 
which it issued. Circulation manifestly advanced in both. Black particles were carried up as 
well as down the neck of the former, the pyrulum, and during their descent, a current was 
obviously conveying black particles up the body of the hydra; something similar seemed to 
be going on in an isolated pyrulum, where there was no hydra. 
“The preceding animals originated and disappeared without leaving any traces behind. 
Indeed the smaller Medusz never leave anything that I have seen. 
Another species (J/edusa duodecilia) has sometimes appeared and decayed mysteriously, 
without affording obvious indications of its origin. This animal occurs in April; the former is 
developed from June until August. It is an eighth of an inch in diameter, with sixteen long, 
slender, tentacular, or ciliary organs, disposed in four bundles, which issue from four marginal 
prominences. At the base of each set is a black speck. The transparence of the Medusa is 
such, that while suspended in equilibrium in the water it is scarcely perceptible. 
“The evolution of the Medusa ocilia is progressive, accelerated perhaps by external 
temperature. It has occurred to me under no other conditions than as above specified. A 
number of whitish corpuscula seem to be generated rather suddenly among the hydre, either 
singly, in pairs, or in clusters of three, four, or five, as already stated. Each is affixed by an 
independent pedicle, and generally about the orifice of a twig of the zoophyte. One, wherein 
no subordinate organic parts were visible, on first inspection, was observed to unfold in three 
hours. 
“There is reason to believe that this Medusa is confined in a diaphanous vesicle or 
involucrum, remaining in its place after the animal has escaped. If actually so, which requires 
confirmation, we cannot but recognise strict analogy to the vesicles of the Sertularia, some 
being hardly perceptible after discharging their contents, from extreme transparency. 
“ A colony, computed at 130 individuals, of the Medusa ocilia was produced in four or 
