One of the most valuable of these, from a scientific point of view, was an essay upon the causes of phosphorescence in the sea, frequently observed in tropical and subtropical regions, but occasionally in European waters.* Of the creature discovered and described by Peron, Phipson says that it is "one of the most curious of animals. It belongs to the tribe of Tunicata.
A very curious instance of reduced bracts, developing to unusual size, is afforded by a variety of corn, which is called Zea Mays cryptosperma, or Zea Mays tunicata. In ordinary corn the kernels are surrounded by small and thin, inconspicuous and membranaceous scales. Invisible on the integrate spikes, when ripe, they are easily detected by pulling the kernels out.
I do not think that we even yet know the precise links of connection between the two; but the investigations of Kowalewsky and others upon the development of Amphioxus and of the Tunicata prove, beyond a doubt, that the differences which were supposed to constitute a barrier between the two are non-existent.
In cryptosperma they are so strongly developed as to completely hide the kernels. Obviously they constitute a case of reversion to the characters of some unknown ancestor, since the corn is the only member of the grass-family with naked kernels. The var. tunicata, for this same reason, has been considered to be the original wild form, from which the other varieties of corn have originated.
Here stagnation and degeneration mean, as a rule, extinction. Of all the relatives of vertebrates back to worms only the very aberrant lines of amphioxus and of the tunicata remain. Of the rest not a single survivor has yet been discovered. And yet what hosts of species must have peopled the sea. The primitive round-mouthed fishes have practically disappeared.
By this is meant the following phenomenon: Certain animals, as the salpa and doliolum of the order of the tunicata, as well as certain mites and many tape-worms, produce offspring which are wholly dissimilar to the mother stock. The plant-lice transmit themselves through six, seven, even ten generations by means of sprouts, until a generation appears which lays eggs.
The thyroid appears in fishes, and Gegenbaur believes that it may have been a useful organ to the Tunicata in their former state of existence. Dr. Clevenger, in the American Naturalist for January, 1884, points out another curious structure in man, whose significance does not seem to have been previously observed. This is a strange and striking fact relating to the formation of the veins.
Here he adopts the investigations of A. Kowalewsky, and the deductions of Häckel founded upon them, concerning the larva of the ascidiæ, a genus of marine mollusca of the order tunicata, and sees in a cord, to be found in this larva, most decided relationship to the spine of the lancelet fish or amphioxus, the lowest of all the vertebrates, it being yet doubtful whether it belongs at all to the vertebrates.
In the North-east Australian province we have species of Donax, Mactra and Corbula, all apparently new, from the shallower localities; Corbula tunicata, Pectunculus tenuicostatus, and another, from 8 to 11 fathoms, off Cumberland Islands; species of Arca, Pectunculus, Avicula, Pecten, Venus, Circe, Cardium, Cardita, and Erycina, mostly new, from 15 to 17 fathoms in a sandy and shelly bottom off Cape Capricorn.