Too Long; Didn't Read

The development of the eyes of game fishes (salmonoids), as is well known, is relatively far advanced before the fish culturist is positively assured that embryos are developing normally in the egg. A method, therefore, which would enable us to shorten this period of probation would not only be desirable, but be also of value under certain circumstances, since it is certainly annoying after having had them in water for four or five weeks, spending time and care over them, to eventually find, when the "eye spots" do not develop, that all our trouble was wasted and that no development at all took place. It is true one may, with proper preparations and with the help of the pocket lens or microscope, follow the development while there may be no external signs of the process evident. This method of making the test is, however, not adapted to the purposes of the practical fish culturist, who will have better success by the following method: If fertilized fish ova are placed in a 50 per cent. solution of wine vinegar [any ordinary vinegar will probably be found to answer just as well--Tr.] the embryo, even during the very first stages of development, will become apparent to the eye lying on the transparent yelk. The acetic acid contained in the mixture, one part water to one part wine vinegar, causes the material of the embryo proper to coagulate, while the yelk remains clear.