The Betardation of the Develojmient of the Ova of the Herring. 1 1 



occur in that capsule. As I pointed out above, the diameter of the 

 zona varies much. In some eggs the two layers of the zona ma}- be 

 seen separated. In one egg here and there the vitelline membrane 

 may be made out. Further, the eggs are differently served by the 

 currents of water. 



It is quite possible that the quality of the water at the Laboratory 

 may be a contributory factor. It is probably charged with organic 

 matter. 



While active embryos are found in eggs containing the crystals, it 

 is not likely that their presence is an advantage. When the crystals 

 are formed in a canal in the embrj^o, the}- will almost surely prove a 

 fatal encumbrance. 



Recommendations. 



If the experiment of transporting the ova of the herring to New 

 Zealand be made, the following would, I think, be a suitable appa- 

 ratus. It is shown in plan in fig. 1. It consists of six compartments, 

 each of which contains a revolving frame. The frame will be able to 

 carry on its external faces four glass plates, 9 inches by 7 inches. A 

 section through two of the compartments is given in fig. 1a. A shaft 

 running longitudinally above the middle of the apparatus would 

 impart the revolving motion to the frames b}^ means of little belts 

 (rubber cord.) 



The amount of water circulated through the apparatus should be as 

 large as possible. If iron pipes are used to cool the water it will 

 probably be better to have ordinary unprotected iron pipes.* In any 

 case, the pipes and apparatus should be well seasoned, by being 

 exposed to the action of sea-water, for some time previous to the 

 experiment being made. The water when it leaves the cooling 

 apparatus should pass into a reservoir, surrounded by ice. Thence it 

 should How through the apparatus. If the water be not used over 

 again, the waste water can be utilized to cool the incoming water. 

 Where the water is to be used over again, a pump will be required to 

 bring it from the reservoir. A small quantity of freshly- cooled water 

 should be steadily added. 



This apparatus should be provided with lids, and should be kept in 

 a dimly-lighted apartment. 



It is most important to have clean water at all times for the spawn. 

 This should be carefull}- arranged when the spawning is taking place, 

 for mud, etc., adhere readily to the ova. Wherever necessary, the 

 water should be filtered through sand. It is hardly possible that all 

 the eggs pressed on to the plates will live. 



Where onlv a small quantity of cooled water is available, it might 

 be advisable to have it sterilized. I have not, however, made any 

 experiments with sterilized water. 



Some precautions should be observed when the spawn is being- 

 obtained. Only spavi-n that runs freely on gentle pressure should be 

 emplo3''ed. Milt and spawn should be preferably obtained from living 

 fishes. The eggs should be arranged thinly on the plate. They 

 should be protected from being touched after they are on the plate. 

 The spawn should be brought into moving water as soon as possible. 



* Vide Davis., "The Action of Water on Zinc and Galvanized Iron." The 

 Journal of Chemical Industry. Vol. XVIII., Feb. 28, 1891>. 



