5i RECOKDS OF THE AUSTRALIAN MUSEUM. 



A marked diiFerence is observable in the relative specific 

 gravity of the eggs of Betta and Polyacanthus.. As previously 

 described those of the former are heavier than water, and the 

 male collects them as they sink and places them beneath the 

 nest. In the latter the eggs are lighter than water, and thus 

 ascend to beneath the bubbles without the aid of the male. At 

 the moment of extrusion the female is quite inverted, so that the 

 eggs, apart from their relative lightness, are directed upwai'ds. 

 As the nest may be of but little extent, say, at first, of the size 

 of a shilling, the eggs frequently rise to the surface in the clear 

 water beyond its margin ; these are collected by the male and 

 placed beneath the bubbles. This does not, however, occur until 

 some little time after the eggs are produced, for, unlike the con- 

 dition in Betta, it is the male who is most exhausted, the female 

 being the first to move away. 



The female Paradise Fish seems to have greater motherly 

 instinct than the female Betta, and frequently takes part in 

 collecting the eggs and placing them in the " cradle," though this 

 is quite subject to the whim of the male, who assumes complete 

 control. 



I now have eight pairs of Polyacanthus breeding, and there is 

 much diffei-ence in the amount of toleration extended to the 

 female by their respective mates. Though I had three nestings 

 of Betta the progeny was the i-esult of but one pair, so that my 

 generalisations in this respect may not be quite fair. The 

 female Betta certainly devoured all eggs and young that came 

 within her reach. One of the female Polyacanthiis, on the other 

 hand, obtained three or four eggs from the nest, evidently with 

 the view, like the male, of rearranging their position. She was, 

 however, driven away, but at the first oppoi'tunity returned the 

 eggs to the nest, having had them in her mouth for more than a 

 minute. 



As I had so many pairs breeding I could afford to sacrifice one 

 family in order to ascertain, if possible, what real object the male 

 has in so zealously tending and guarding the eggs. To this end, 

 as soon as a complement of eggs was pi'oduced I removed them 

 en masse, by means of a tablespoon, to another vessel. They 

 hatched in the usual course, and the larva3 developed, so that now, 

 at the end of six weeks, they are as lai'ge, active and healthy as 

 those left under the care of the male. 



With the view of asceitaining the function of the bubbles, I 

 removed from another nest some of the newly-deposited eggs, and 

 carefully rejected all bubbles. As before, these eggs de^^eloped 

 equally with those left under paternal care. It would seem, 



