EXPERIMENTAL WORK. 165 



living, and had a duplicate set of slate trays ; and the next 

 morning I placed a rearing-box for them below Craigend dam. 

 This is the last reference to them in the note-book. The results 

 they established are, that Loch Leven and burn can be crossed, 

 and that the fry produced are as strong and healthy as the pure- 

 bred fry ; this was the object of the set. Experiment 3 points 

 to the possibility of a very young male causing the embryo to 

 hatch later than usual. This is the key to imperfect impregna- 

 tion. It is also shown that there was no perceptible difference 

 between the Loch Leven eggs milted by a small burn-trout 

 (Experiments 1, 2, and 3) and burn-trout eggs milted with Loch 

 Leven milt (Experiment 4), up to the clear development of the 

 embryotic line. This does not take us very far, but it is interest- 

 ing as the beginning of a series of experiments which have already 

 spread over twelve years. There is another result, not contem- 

 plated at the time, and the importance of which was not realised 

 until afterwards, when I read in Stone the account of M. Vrassky's 

 experiments. Milt was capable of impregnating ova if kept in 

 a carefully dried and well-corked tube ; and ova were capable of 

 receiving impregnation, if spawned into a dry bottle, many hours 

 after having been taken. The dry process of impregnation follows 

 as a necessary corollary. This dry process I had always used, not 

 knowing I was singular, in this country at least, in using it. I 

 had commenced with my first spawner, and, having found it 

 answer, never thought any more about it. 



On November 5th I went to Kinross, to obtain Loch Leven 

 trout ova, and tried the following experiment : 



Experiment 6. 



A spawner of about 1 Ib. weight yielded her eggs with a 

 copious flow of red liquid (possibly the fish had been injured in 

 netting). The eggs flowed easily, and were to all appearance ripe ; 

 one, but only one, egg was covered with a bloodshot membrane, 

 showing the fish was newly ripened. I was anxious to ascertain 

 whether such ova were capable of being impregnated. I took the 

 ova in a spawning-dish, and milted with a free- running male, and 



