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The difference of appearance between fertilized and unfertilized ova treated by the method will demonstrate its utility. Whoever does not trust to the method for the evidence of death of the eggs until after five weeks subsequent to impregnation, must of course wait. Director Tiefenthaler, of Koelzen, has had the kindness to test the method practically, and finds it useful to fish culturists.
Of these polypi, in a large specimen, there must be many thousands; yet we see that they act by one movement: they have also one central axis connected with a system of obscure circulation, and the ova are produced in an organ distinct from the separate individuals.
In the lower Vertebrates the formation of ova in the germ-epithelium of the ovary continues throughout life; but in the higher it is restricted to the earlier stages, or even to the period of embryonic development. However, the number of ova in the two ovaries is very large in the young girl; there are calculated to be 72,000 in the sexually-mature maiden.
See the ova only and consider the second ovum as the first two ova's means not of reproducing themselves but of continuing themselves repeating themselves the intermediate lives being nothing but, as it were, a long potato shoot from one eye to the place where it will grow its next tuber.
Let the water run through and over all your ponds and apparatus for as long as possible before you begin operations. Everything should now be ready for the reception of the ova. The rearing boxes are resting upon stones placed at the bottom of the ponds, with the edges some six inches above the level of the water, and moored to the sides to prevent their being moved by the current.
Large unicellular organisms like the Amoebae were found creeping about inside the body of the sponge, and were thought to be parasites. It was afterwards discovered that they were really the ova of the sponge from which the embryos were developed.
Crossings of these species took places in 1880, and, as I stated before, the ova obtained from a long pairing between a Ceanothi female with a Gloveri male, were the only ones which were fertile. The Gloveri cocoons received in 1880 were of a very inferior quality, and produced moths from which no pairings could be obtained, although some crossings took place.
We see, therefore, how extremely important is the function of the testis. Its significance is not alone for the race, it is not simply concerned with the formation of the spermatozoa which share equally with the ova the honor of making the mankind of the future. It also has a separate and distinct function which has reference to the individual.
Milt from a ripe male fish is then allowed to run over the ova in the dish, and is made to run well between them by tilting the dish about from side to side. The ova will now adhere together, and some water should be added.
When Ramsbottom was in Galway he caught a large Trout, out of whose throat he squeezed a thousand ova, which were deposited in a spawning-box, many of which came to life notwithstanding the pit they had escaped from. Yet, in addition to them, are all the Par, Bullheads, Eels, Loaches, and aquatic larvae which may be found swarming in every spawning bed by any one who will look for them.
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