It is obvious that the hatching of the young as a larva necessitates h After Heymons, Zeit.
Supposing this could be established, the question would still remain whether the same result could not be obtained at far less expense by dispensing with the hatching operations and distributing the eggs directly after fertilization.
In moths and certain saw-flies there is no rupture of the membranes; the Russian zoologists Tichomirov and Kovalevsky have described the growth of both amnion and embryonic ectoderm around the yolk, the embryo being thus completely enclosed until hatching time by both amnion and serosa.
During the first month after hatching, 34 to 36 mm.
Of these, Forty Hall, in splendidly timbered grounds, is from the designs of Inigo Jones; and a former mansion occupying the site of White Webbs House was suspected as the scene of the hatching of Gunpowder Plot.
Jaws under Hexapoda); in the presence of a large number of excretory (Malpighian) tubes; in the firm texture of the forewings; in the presence of appendages (cerci) on the tenth abdominal segment; and in the absence of a metamorphosis, the young insect after hatching closely resembling the parent.
Russia, justly offended, drew closer her ties with Prussia, where Bismarck was already hatching the plans which were to mature in 1866; and, if the attitude of Napoleon in the Polish question prevented any revival of the alliance of Tilsit, the goodwill of Russia was assured for France in the coming struggle with Austria in Italy.
The earlier advocates of artificial propagation and fish-hatching seem to have been under the impression that the thousands of fry resulting from a single act of artificial propagation meant a corresponding increase in the numbers of edible fish when once they had been deposited in suitable waters; and also that artificial fertilization ensured a greater proportion of fertilized eggs than the natural process.
In the United States the utility of the cod-hatching operations has been constantly asserted by representatives of the Bureau of Fisheries, but practically the only evidence adduced is the occasional appearance of unusual numbers of cod in the neighbourhood.
It has not been established that the fluctuations in the local cod fisheries bear any fixed relation to the extent of the hatching operations, while the earlier reports of the Commissioners of Fisheries contain evidence that similar fluctuations occurred before the hatching of "fish commission cod" had begun.
The most exact investigations bearing upon this problem are those which have been recently undertaken in Norway in connexion with the cod-hatching operations at Arendal under Captain Dannevig.
In a younger stage of their development, however, the young are carried in a temporary abdominal pouch, to which they are transferred after hatching, and into which open the mammary glands.
The vernacular name barnacle, traceable to the fable of pedunculate cirripedes hatching out into bernicle geese, has also been transferred to the sessile cirripedes, which are popularly known as acorn barnacles.
Eggs produced in the autumn by fertilized females remain on the plant through the winter and hatching in the spring give rise to female individuals which may be winged or wingless.
The irritation set up by the hatching egg and its resulting larva appears to be the stimulus to development, and net a poison or enzyme injected by the insect.
As regards growth after hatching, all beetles undergo a "complete" metamorphosis, the wing-rudiments developing beneath the cuticle throughout the larval stages, and a resting pupal stage intervening between the last larval instal1 and the imago.
In the case of certain beetles whose larvae do not find themselves amid appropriate food from the moment of hatching, but have to migrate in search of it, an early larval stage, with legs, is followed by later sluggish stages in which legs have disappeared, furnishing examples of what is called hypermetamorphosis.
The wings of insects are, in all cases, developed after hatching, the younger stages being wingless, and often unlike the parent in other respects.
Growth And Metamorphosis After hatching or birth an insect undergoes a process of growth and change until the adult condition is reached.
These differences in larval form depend in part on the surroundings among which the larva finds itself after hatching; the active, armoured grub has to seek food for itself and to fight its own battles, while the soft, defenceless maggot is provided with abundant nourishment.
The eggs of locusts may remain for years in the ground before hatching; and there may thus arise the peculiar phenomenon of some species of insect appearing in vast numbers in a locality where it has not been seen for several years.
At hatching far more developed than are those of the herons or the cormorants; and, in a general way, nearly every one of the asserted peculiarities of the two subclasses breaks down under careful examination.
From Lankester's Treatise on The life history of the order is almost un Zoology, part iv.) k nown, but at the time of hatching the young FIG.
Lacinularia racemovata and Conochilus form free floating aggregates, the eggs, as laid, hatching and the young settling among the approximated gelatinous tubes of the parents.
Pieces of paper punctured with small holes are placed over the trays in which the hatching goes on; and the worms, immediately they burst their shell, creep through these openings to the light, and thereby scrape off any fragments of shell which, adhering to the skin, would kill them by constriction.
The amount of nourishment required for this rearing is as follows: hatching to first moult, about 9 lb of leaves of tender growth, equal to 40 to 45 lb ripe leaves; first to second moult, 24 lb, representing roc) lb ripe leaves; second to third moult, 80 lb, representing 240 lb ripe leaves; third to fourth moult, 236 lb, representing 472 lb ripe leaves; fourth moult to mounting, 1430 lb, representing 1540 lb ripe leaves, totalling to about one ton of ripe leaves for a complete rearing.
In 1750, and again, it is thought, in 1754, he was in London, hatching futile plots and risking his safety for his hopeless cause, and even abjuring the Roman Catholic faith in order to further his political interests.
The Nile crocodile makes a hole in white sand, which is then filled up and smoothed over; the mother sleeps upon the nest, and keeps watch over her eggs, and when these are near hatching - af ter about twelve weeks - she removes the 18 in.
As soon as ten or a dozen eggs are laid, the cock begins to brood, always taking his place on them at nightfall surrounded by the hens, while by day they relieve one another, more it would seem to guard their common treasure from jackals and small beasts of prey than directly to forward the process of hatching, for that is often left wholly to the sun.'
The second, and more familiar, type of pisciculture is that known as fish-hatching, with which must be associated the various methods of artificial propagation.
The hatching of eggs, whether of fresh-water or salt-water fishes, presents no serious difficulties, if suitable apparatus is employed; but the rearing of fry to an advanced stage, without serious losses, is less easy, and in the case of sea-fishes with pelagic eggs, the larvae of which are exceedingly small and tender, is still an unsolved problem, although recent work, carried out at the Plymouth laboratory of the Marine Biological Association, is at least promising.
Upon hatching, the young, which differ from the adult in possessing long antennae and a pair of powerful fossorial anterior legs, fall to the ground, burrow below the surface, and spend a prolonged subterranean larval existence feeding upon the roots of vegetation.
The blackcock then rejoins his male associates, and the female is left to perform the labours of hatching and rearing her young brood.
Under favourable conditions, when food is obtainable, growth is rapid, the time from the hatching of the young until it reaches maturity and dies after oviposition being, for example, about eleven weeks in R.
Very few Crustacea are viviparous in the sense that the eggs are retained within the body until hatching takes place (some Phyllopoda), but, on the other hand, the great majority carry the eggs in some way or other after their extrusion.
Within the egg (or within the maternal brood-chamber), so that the larva, on hatching, has reached a stage more advanced than the nauplius.
In fresh-water culture little advantage, if any, has been found to result from artificial hatching, unless this is followed by a successful period of rearing.
These establishments have been principally devoted to the hatching of the eggs of plaice.
For a summary of these investigations see papers on "Artificial Fish-hatching in Norway," by Captain Dannevig and Mr Dahl, in the Report of the Lancashire Sea Fisheries Laboratory for 1906 (Liverpool, 1907).
It would thus seem clear that the attempts hitherto made to increase the supply of sea-fish by artificial hatching have been unsuccessful.
The energy and money devoted to hatching operations should be diverted to the serious attempt to discover a means of rearing on a large scale the just-hatched fry of the more sedentary species to a sturdy adolescence.
The ectoderm is indicated by close hatching, the endoderm by light hatching, the mesogloea by thick black lines, the horny skeleton of the pneumatophore and sail by dotting.