72 NATURAL SCIENCE. Jan., 1895. 



the Nepean River at Camden, by Mr. H. J. McCooey, I found six fine specimens of 

 Macquarie's Perch, and I am, therefore, compelled to break the last link of 

 exclusiveness to which the Murray system could lay claim. That a fish of such 

 size and excellence could exist in numbers so near to the metropolis, yet be quite 

 unknown from that locality to Australian scientists, shows how sadly our fresh- 

 water fauna has been neglected, and the necessity for paying more particular 

 attention to this branch of zoological science henceforth. 



Australian Museum, Sydney, J. Douglas Ogilby. 



6th Oct., 1894. 



The Claws of Arch.eopteryx. 



In one of his very interesting articles on Archa-opteryx, Mr. Pycraft has suggested 

 that the wing-claws were used mainly during youth, as the young Hoatzin uses his 

 now, to assist him in climbing. This will hardly account for the maintenance of 

 the great size of the claws after the attainment of maturity. May they not have 

 been useful while moulting was in process ? It is hardly likely that this very 

 primitive bird had developed a perfect system of moulting, by which the quills 

 were shed in pairs at considerable intervals, as they are by most birds now. Ducks 

 shed their large quills almost simultaneously, and take refuge from enemies on the 

 water. But a land bird, even if fairly strong in the leg, might find assistance from 

 his forelimbs useful in climbing up trees, in order to get out of the reach of enemies 

 of non-arboreal habits. 



F. W. Headley. 



Evolution of a Protective Habit in Sea-Urchins. 

 With reference to the very interesting note in the September number of 

 Natural Science, entitled " A Moving Grove," it may be pointed out that another 

 species of the sea-urchin Hipponoe, namely H. variegata, has a somewhat similar 

 habit to H. esculenta. That is to say, it carries portions of seaweed on the spines of 

 its anal region. It is conjectured by Studer, who relates the fact, that this seaweed 

 is for the animal to stick its eggs to — a kind of artifical brood-pouch. This forms 

 an interesting stage in the development of a habit, and suggests that in habits as in 

 structures, for which we are at first unable to account by mere Natural Selection, 

 much may be explained by a change of function. The earlier stages may have been 

 evolved in obedience to conditions quite different from those that have governed the 

 later stages. ' B. 



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