14. DEVELOPMENT. 
as life departs. The same phenomenon is exhibited by the hydroid, helianthoid, and asteroid 
polypes. Ifa bunch of one of the bushy corallines, such as Sertudaria abietina, be plunged 
when alive and active into fresh water or spirits, a gorgeous display of living stars is instan- 
taneously produced. So also with Pennatula phosphorea.* 
The light of the Medusze, as Spallanzani observed, is not given out by all parts of the 
body indifferently, but only by certain structures. Spallanzani states that when he cut off 
the margins of the Pelagia phosphorea to a depth of from 5 to 6”, the border continues to 
shine, which is not the case with the disk, and he attributes the phenomenon to the produc- 
tion of a phosphorizing mucus by the light-producing parts. | Ehrenberg regards the light as 
an act of organic life. He observes that ‘‘ the active organic phosphorescence appears 
frequently periodically, produced either spontaneously, or by excitement, frequently as 
rapidly produced sparks, resembling small electric discharges. This repeated sparkling 
converts a mucous, gelatinous fluid, which is discharged more abundantly during the operation, 
into a secondary state of phosphorescence, which continues for a time, even after the death of 
the organism, or after the severing of its parts.” He considers the mucus enveloping the 
ovaries as particularly susceptible, when in a fresh state, to this imparted phosphorescence. 
In Oceania pileata he observed the light emanate from the locality of the ovaries, which, 
being pendant in the centre of the sub-umbrella, illuminated the animal as an argand lamp 
illuminates its glass shade. In Zhaumantias hemispherica he observed the light to be given 
out by the bulbous bases of the tentacula, which formed a garland of sparks of fire around 
the circumference of the umbrella. Macartney had previously noticed, as we have seen, that 
in this naked-eyed species, the light was given out from the same spots, and, he adds, from 
the centre also. I have observed that in Thawmantias lucida the light was invariably given 
out by the bulbs of the tentacles, and so also in other species of the same genus. In the 
Dianea appendiculata, which is a beautifully luminous species, the phosphorescence is of a 
greenish hue, and appears to radiate from the reproductive glands. In the Mediterranean I 
have seen a large Mesonema give out rich flashes of flame from the bases of its numerous 
marginal tentacles. Both Spallanzani and Tilesius have noticed that the light in the higher 
Meduse shone most vividly during the contractions of the umbrella. 
Taking one fact with another, it would seem that the phosphorescence in the naked-eyed 
Medusz is developed by the reproductive and motor systems: how, we cannot say. 
Ehrenberg has concluded that the production of the light is ‘a periodical vital act dependent 
on the nervous system, and similar to the development of electricity.” But this can only be 
regarded as an hypothesis. We have no clear evidence yet of the presence of a nervous 
system in these animals. 
Development.—When treating of the reproductive organs of these animals, I discussed 
the ovarian and spermatic glands; but the naked-eyed Medusze do not reproduce their 
species only in the normal fashion, i. e. by fecundated eges ; several of them are now known 
to multiply their kind by gemmation, little ones springing out almost ready made from the 
substance of their parents, as Minerva budded on the creative brain of Jupiter. This mode 
t * See a notice of the phenomena exhibited by this zoophyte when phosphorescing, in the second 
edition of Dr. Johnston’s British Zoophytes. 
