IX ZOOPHYTES 211 



moves its wings alternately, instead of both together, as in other 

 birds. These clumsy, loggerheaded 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 : and the Apteryx 

 of New Zealand, as well as its gigantic extinct prototype the 

 Deinornis, possess only rudimentary representatives of wings. 

 The steamer is able to dive only to 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 sur- 

 prisingly heavy and strong : the head is so strong 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 in the evening pluming themselves in a 

 flock, they make the same odd mixture of sounds which bull- 

 frogs do within the tropics. 



In Tierra del Fuego,as well as at the Falkland Islands,! made 

 many observations on the lower marine animals,^ but they are 

 of little general interest. I will mention only one class of facts, 

 relating to certain zoophytes in the more highly organised divi- 

 sion of that class. Several genera (Flustra, Eschara, Cellaria, 

 Crisia, and others) agree in having singular movable 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 than in a real bird's 

 beak. The head itself possesses considerable powers of move- 

 mept,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 



1 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 ribl)on, on the most moderate computation there were six 

 hundred thousand eggs. Yet this Doris was certainly not very common : although 

 I was often searching under the stones, I saw only seven individuals. A^o fallacy is 

 more common wilh naturalists^ than that the numbers of an individual species depend 

 on its powers of propagation. 



