206 Transactions. — Zoology. 



Occasionally, but not often, we have found a female give eggs of a light 

 straw colour, and these have hatched out quite as well as those of the 

 ordinary hue, with no difference in time, or in the appearance of the fry. 

 On August 28th, 1880, we had in the hatching boxes at Opoho, ova of this 

 colour from two females of 51bs each, it was also much smaller than the 

 pink ova from equally heavy female trout. This peculiarity in colour has 

 been observed to occur sometimes with trout in English rivers, as mentioned 

 by Mr. Frank Buckland, in his book on " Fish Culture." In this last 

 season's stripping one female gave 30 eggs much larger, twice the diameter 

 of her other eggs, and as big as Califoruian salmon ova. They were of a 

 light violet colour, and most hatched out, but 17 only survived, and these 

 are thriving well and are kept by themselves. Her other ova were of the 

 usual size and colour. 



As to the number of ova produced by our trout, we find it to be 800 to 

 1000 for every pound weight of the fish. 



Hatching boxes. — The hatching boxes and house, dam, and ponds for the 

 young fish, are on the banks of the Opoho Creek, at the north end of Dun- 

 edin. The place is awkward of access, but excellently chosen as regards 

 coldness of water and protection from the sun's rays. The creek, flowing as 

 it does down the shady side of Signal Hill and through bush, is cold, but 

 has a considerable quantity of vegetable matter in solution (see analysis given 

 above) ; not too much, however, as we have found, by the health and success 

 attending our young fish, reared in it. The arrangement of these breeding 

 ponds and the water supply is shown by a diagram which I have made to 

 accompany this paper (pi. XIV). The water passes from the dam through a 

 small fluming of timber four inches by four inches, past the hatching house 

 to the fish ponds, and after flowing through these is allowed to discharge 

 into the creek. At the hatching house a small pipe connects this fluming 

 and the filter-box. The filter-box consists of two chambers, into the first 

 of which, containing the filtering materials, the water flows from the box 

 fluming. The water then passes through the bottom of the partition into 

 the second chamber, where it rises and is drawn off by the several pipes as 

 wanted, which supplies the hatching boxes. These boxes, twelve inches by 

 six inches, built of planks one inch thick, and from four to seven feet long, 

 are placed in parallel rows on either side of the hatching house. Each has 

 sufficient inclination given to it to secure a gentle flow of water, the water 

 passing through a zinc grating from one box to another. Clean gravel 

 about an inch deep, being the debris of trap rock from the Opoho Creek, 

 covers the bottom of each box, and the water, to the depth of two inches, 

 covers this layer. The hatching house is boarded with Hobart Town 

 palings, and has a calico or scrim roof resting on battens. 



