OCR Text |
Show 258 FALKLAND I SL .\NDS. March, 1834. duck escapes when pursued by a dog; but I am nearly sure that the steamer moves its wings alternately, instead of both together, as in other birds. These clumsy, loggerhead~d ducks make such a noise and splashing, that the effect IS exceedingly curious. Thus we find in South America three birds, which use their wings for other purposes besides flight: the penguin as fins, the steamer as paddles, and the ostrich as sails to a vessel. The steamer is able to dive only a very short distance. It feeds entirely on shell-fish from the kelp and tidal rocks; hence the beak and head, for the purpose of breaking them, are surprisingly heavy and strong. So strong is the head, that I have scarcely been able to fracture it with my geological hammer; and all our sportsmen soon discovered how tenacious these birds were of life. When pluming themselves in the evening in a flock, they make the same odd mixture of sounds which bullfrogs do within the Tropics. In Tierra del Fuego, as well as at the Falkland Islands, I made many observations on the lower marine animals,* but they are of little general interest. I will only mention one class of facts, relating to certain zoophytes in the more highly organized division of that class. Several genera (jlustra, eschar a, celtaria, crisia, and others) agree in having singular • While at the Falklands, during the autumn of the southern hemisphere, most of the lower marine animals were breeding. I was surprised to find on counting the eggs of a large white Doris (this sea-slug was three and a half inches long) how extraordinarily numerous they were. From two to five eggs (each three-thousandths of an inch in diameter) were contained in a spherical little case. These were arranged two deep in transverse rows forming a ribbon. The ribbon adhered by its edge to the rock in an oval spire. One, which I found, measured nearly twenty inches in length and half in breadth. By counting how many balls were contained in a tenth of an inch in the row, and how many rows in an equal length of the ribbon, on the most moderate computation there were six hundred thousand eggs. Yet this Doris was certainly not very common: although I was otten searching under the stones I saw only seven indi. viduals. March, 1834. COMPOUND ANIMALS. 259 moveable organs, like those of FLustra avicularia (found in the European seas), attached to their cells. The organ, in the greater number of cases, very closely resembles the head of a vulture ; but the lower mandible can be opened much wider, so as to form even a straight line with the upper. The head itself possesses considerable powers of movement, by means of a short neck. In one zoophyte the head itself was fixed, but the lower jaw free : in another it was replaced by a triangular hood, with a beautifully-fitted trap-door, which evidently answered to the lower mandible. A species of stony eschara had a structure somewhat similar. In the greater number of species, each shell was provided with one head, but in others each had two. The young cells at the end of the branches necessarily contained quite immature polypi, yet the vulture-heads attached to them, though small, were in every respect perfect. When the polypus was removed by a needle from any of the cells, these organs did not appear in the least affected. When one of the latter was cut off from a cell, the lower mandible retained its power of opening and closing. Perhaps the most singular part of their structure is, that when there were more rows of cells than two, both in a Flustra and an Eschara, the central cells were furnished with these appendages, of only one-fourth the size of the lateral ones. Their movements varied according to the species :-in some I never saw the least motion; while others, with the lower mandible generally wide open, oscillated backwards and forwards at the rate of about five seconds each turn; others moved rapidly and by starts. When touched with a needle the beak generally seized the point so firmly, that the whole branch might be shaken. These bodies have no relation whatever with the production of the gemmules. I could not trace any connexion between them and the polypus. From their formation being completed before that of the latter; from the independence of their movements; from the difference of their size in different parts of the branch ; I have little doubt that in their s 2 |