I incline to compare Loeb's parthenogenesis with the development (and of course accompanying cell-division) of dormant buds on stems which have been cut back.
This parthenogenesis has been noticed in several species.
I thought on the subject, but gave up investigating what had been observed, because the female bee by parthenogenesis produces males alone.
A second objection was that the eggs caused to develop by the methods of artificial parthenogenesis could never reach the adult stage and that hence the phenomenon was merely pathological.
If we disregard the cases of parthenogenesis and the X chromosomes, we may state that each species is characterized by a definite number of chromosomes, e.
The action of acids in the mechanism of artificial parthenogenesis provides some interesting physiological problems.
This cannot well be due to the fact that the egg develops; for the writer found some time ago that eggs of Strongylocentrotus purpuratus which are induced to develop by means of artificialparthenogenesis can be fertilized by sperm.
Driesch compared the size of the mesenchyme cells in a sea-urchin embryo produced by artificial parthenogenesis with those of a normally fertilized egg and found them half of the size of the latter.
This new or improved method of artificialparthenogenesis is as follows: The eggs are put for from two to four minutes into 50 c.
No such fusion of two nuclei takes place in artificial parthenogenesis since no spermatozoon enters the egg, and it became necessary, therefore, to abandon Hertwig's definition as wrong.
This makes the proof conclusive that the methods of artificial parthenogenesis can result in the production of normal organisms which can reach the adult stage.
The writer has shown that the same chemical substances which will induce membrane formation and artificial parthenogenesis will as a rule also cause a swelling and liquefaction of the chorion.
Except for the relatively rare instances of parthenogenesis a new individual, whether plant or animal, arises as the joint product of two sexual cells derived from individuals of different sexes.
More recent research has shown that this is due to a peculiar form of parthenogenesis (cf.
Bataillon's discovery is that we have now an experimental demonstration of parthenogenesis in a vertebrate animal, and in one so highly organised as the frog.
But the interdependence of the sexes is so far from being a new fact that it is as old as the evolution of sex, and the decadence and disappearance of parthenogenesis or reproduction from the female sex alone.
This forced parthenogenesis which I have described seems to be a phenomenon with which botanists are unfamiliar.
In ordinary parthenogenesisthe fruit grows without any pollen influence at all.
Until I learn that it has been described and named by others I shall call it Allergic Parthenogenesis (Allos, ergon).
Parthenogenesis without heterogamy occurs in a large number of forms.
A strong support for this hypothesis would be afforded were it to be definitely established that a polar body is not formed in the Arthropoda and Rotifera; since the normal occurrence ofparthenogenesis is confined to these two groups.
In the cases of true heterogamy parthenogenesis has become confined to special generations, which differ in their character from the generations which reproduce themselves sexually.
The transformation of heterogeny into pure parthenogenesis has obviously been produced by other causes as well as by those mentioned in the main part of this paper.
As soon, however, as the second nuclear spindle is formed, parthenogenesis becomes impossible.
But I may add that we have also succeeded in directly proving the occurrence of parthenogenesis in Rotifera, as will be described in detail in another paper.
In the animal kingdom, such a condition chiefly occurs in species of which the closely-allied forms exhibit the above-mentioned alternation between parthenogenesis and amphigony, viz.
Pure parthenogenesismay be produced without the intermediate condition of heterogeny.
On the other hand, an egg which does not expel its male part may develope without fertilization, and thus we are led to the obvious conclusion that parthenogenesis is based upon the non-expulsion of polar bodies.
Parthenogenesis takes place when the whole of the ancestral germ-plasms, inherited from the parents, are retained in the nucleus of the egg-cell.
Siebold, "On a True Parthenogenesis in Moths and Bees; "F.
Parthenogenesis (division and development of an egg without the agency of male sperm) has been brought about artificially by Jacques Loeb in species as complicated as frogs.
Parthenogenesis (development of eggs without agency of male sperm) proves that in many simple forms the female nucleus alone possesses all the essential determiners for a new individual.
Like the plant-lice or drones, the mammifers called man are subject to alternate generation, one parthenogenesis always separating the veritable conjunction of the differentiated elements.
All that one sees is that parthenogenesis is always transitory, and that after a number of virginal generations, normal fecundation always intervenes.
Normal parthenogenesis belong equally to summary and to complicated animals, to wheel-animals and to bees.
The queen bee lays both fecundated and non-fecundated eggs; the first hatch female, the second invariably male, here the male element would seem to be the product of parthenogenesis and the female to require previous fecundation.
Human parthenogenesis is less absurd: it offers an order, and promiscuity is a disorder.
This provoked parthenogenesis is neither more nor less interesting than the normal.
The equivalence of the germ nuclei in development is shown by the experiments on the fertilization of enucleated eggs and artificial parthenogenesis already referred to.
Parthenogenesis in the Tenthredinae; in Cynipidae; in Crustacea.
I speak of the matter as parthenogenesis in advance of microscopic examination of the ovules,--which will be made next year; but parthenogenesis seems to be the most likely explanation.
We can speak of parthenogenesis only when the embryo originates from a female gamete alone, i.
But this is not a universal rule, for in some cases of parthenogenesis polar bodies are extruded in the usual way (Aphis, some Lepidoptera), and in some fertilized eggs the polar bodies are retained in the ovum.
Phenomena of the nature of parthenogenesis have never been observed in the male gamete, but it has been suggested by A.
In some Insecta and Crustacea exceptional parthenogenesis occurs: a certain proportion of the eggs laid are capable of undergoing either the whole or a part of development parthenogenetically, e.
Fecundity, longevity and parthenogenesisof the American roach, Periplaneta americana L.
Here again parthenogenesis continues for generation after generation so long as conditions are favourable, i.
Parthenogenesis occurs when food supply is plentiful and temperature high.
The ova developing by parthenogenesis and giving rise to males segment in the usual way, and all the cells both of soma and gametocytes contain only N chromosomes.
It has already been stated that both parthenogenesis and gemmation are ultimately derived from sexual reproduction.
The rapidity of the effects of selection seems to preclude the explanation that pseudo-parthenogenesis has complicated the results.
Whether pseudo-parthenogenesis that Woodruff and Erdmann have found occurring in paramecium at intervals involves a redistribution of the hereditary factors is not clear.
More light on this, as on other points, may probably be thrown by further investigations on parthenogenesis and the presence or absence of a polar cell in eggs which develop parthenogenetically.
Arthropoda and Rotifera, where polar cells are not formed, and an essential part of the nucleus not therefore removed, parthenogenesis can much more easily occur than when polar cells are formed.
That the part removed in the formation of the polar cells is not absolutely essential, seems at first sight to follow from the fact of parthenogenesis being possible in instances where impregnation is the normal occurrence.
But Loeb[4] succeeded in obtaining a full development by treating the eggs of echinoderms with chloride of magnesium; thus artificial parthenogenesis had been discovered.
Later researches have shown that artificial parthenogenesis may occur in all classes of the animal kingdom and may be provoked by all sorts of chemical or physical means.
In the first place, we do not know whether parthenogenesis may not finally settle down into complete asexual reproduction.
Seidlitz is an exception, since in his work on Parthenogenesis (Leipzig, 1872, p.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "parthenogenesis" in a variety of sentences. We hope that you will now be able to make sentences using this word.
