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Haeckel and
late 20th and early 21st century critics, Jonathan Wells and Stephen Jay Gould, have objected to the continued use of Haeckel s embryo drawings in textbooks.
Haeckel s illustrations show vertebrate embryos at different stages of development, which exhibit embryonic resemblance as support for evolution, recapitulation as evidence of the Biogenetic Law, and phenotypic divergence as evidence of von Baer s laws.
The series of twenty-four embryos from the early editions of Haeckel s Anthropogenie remain the most famous.
Similarities can be seen along the first two rows ; the appearance of specialized characters in each species can be seen in the columns and a diagonal interpretation leads one to Haeckel s idea of recapitulation.
Ernst Haeckel, along with Karl von Baer and Wilhelm His, are primarily influential in forming the preliminary foundations of ‘ phylogenetic embryology based on principles of evolution.
Haeckel sBiogenetic Law portrays the parallel relationship between an embryo s development and phylogenetic history.
The term, ‘ recapitulation ,’ has come to embody Haeckel s Biogenetic Law, for embryonic development is a recapitulation of evolution.
Haeckel portrays a concrete demonstration of his Biogenetic Law through his ‘ Gastrea theory, in which he argues that the early cup-shaped gastrula stage of development is a universal feature of multi-celled animals.
As a response to Haeckel s theory of recapitulation, von Baer enunciates his most notorious laws of development.
Wilhelm His was one of Haeckel s most authoritative and primary opponents advocating physiological embryology.
His depiction of embryological development strongly differs from Haeckel s depiction, for His argues that the phylogenetic explanation of ontogenetic events is unnecessary.
Although Haeckel is proven right about the allantois, the utilization of Krause s embryo as justification turns out to be problematic, for the embryo is that of a bird rather than a human.
In response to Haeckel s evolutionary claim that all vertebrates are essentially identical in the first month of embryonic life as proof of common descent, His responds by insisting that a more skilled observer would recognize even sooner that early embryos can be distinguished.
Haeckel s opponents believe that he de-emphasizes the differences between early embryonic stages in order to make the similarities between embryos of different species more pronounced.
Although Rutimeyer did not denounce Haeckel s embryo drawings as fraud, he argued that such drawings are manipulations of public and scientific thought.
As a pioneer in mammalian embryology, he was one of Haeckel s strongest critics.
Nevertheless, Bischoff s main argument was in reference to Haeckel s drawings of human embryos, for Haeckel is later accused of miscopying the dog embryo from him.

Haeckel and s
Throughout Haeckel s time, criticism of his embryo drawings was often due in part to his critics ' belief in his representations of embryological development as “ crude schemata .” In this way, Haeckel specifically selected relevant features to portray in his drawings.
Haeckel s opponents found his methods problematic because such simplification eliminates certain structures that differentiate between higher and lower vertebrates.
In 1877, Rudolf Virchow ( 1821 – 1902 ), once an inspiration to Haeckel at Würzburg, proclaimed that Haeckel s embryo drawings represent mere hypotheses.

Haeckel and embryo
Romanes ' 1892 copy of Ernst Haeckel's allegedly fraudulent embryo drawings ( this version of the figure is often attributed incorrectly to Haeckel ).
In addressing his embryo drawings to a general audience, Haeckel does not cite any sources, which gives his opponents the freedom to make assumptions regarding the originality of his work.
The debate between Haeckel and His ultimately becomes fueled by the description of an embryo that Wilhelm Krause propels directly into the ongoing feud between Haeckel and His.
Ultimately, His goes so far as to accuse Haeckel of “ faking ” his embryo illustrations to make the vertebrate embryos appear more similar than in reality.
Rutimeyer claimed that Haeckel “ had taken to kinds of liberty with established truth .” Rutimeyer claimed that Haeckel presented the same image three consecutive times as the embryo of the dog, the chicken, and the turtle.
Romanes's 1892 copy of Ernst Haeckel's controversial embryo drawings ( this version of the figure is often attributed incorrectly to Haeckel ).
For example, Haeckel proposed that the pharyngeal grooves between the pharyngeal arches in the neck of the human embryo resembled gill slits of fish, thus representing an adult " fishlike " developmental stage as well as signifying a fishlike ancestor.
Haeckel produced several embryo drawings that often overemphasized similarities between embryos of related species.
Ernst Haeckel ( 1866 ), in his endeavour to produce a synthesis of Darwin's theory with Lamarckism and Naturphilosophie, proposed that " ontogeny recapitulates phylogeny ," that is, the development of the embryo of every species ( ontogeny ) fully repeats the evolutionary development of that species ( phylogeny ), in Geoffroy's linear model rather than Darwin's idea of branching evolution.
The presence of gill-like slits in the neck of the developing human embryo famously led Ernst Haeckel to postulate that " ontogeny recapitulates phylogeny "; this hypothesis, while false, contains elements of truth, as explored by Stephen Jay Gould in Ontogeny and Phylogeny.

Haeckel and drawings
On the other hand, Michael K. Richardson, Professor of Evolutionary Developmental Zoology, Leiden University, while recognizing that some criticisms of the drawings are legitimate ( indeed, it was he and his co-workers who began the modern criticisms in 1998 ), has supported the drawings as teaching aids, and has said that " on a fundamental level, Haeckel was correct "
In his drawings, Haeckel cites the notochord, pharyngeal arches and clefts, pronephros and neural tube as palingenetic features.
Haeckel was not the only one to create a series of drawings representing embryonic development.
Michael Richardson and his colleagues in a July 1997 issue of Anatomy and Embryology, demonstrated that Haeckel fudged his drawings in order to exaggerate the similarity of the phylotypic stage.
In a March 2000 issue of Natural History, Stephen Jay Gould argued that Haeckel “ exaggerated the similarities by idealizations and omissions .” As well, Gould argued that Haeckel s drawings are simply inaccurate and falsified.
Some version of Haeckel s drawings can be found in many modern biology textbooks in discussions of the history of embryology, with clarification that these are no longer considered valid.
" Moreover, " vertebrate embryos, for most of the longest period of middevelopment, do look remarkably alike, pretty much, but not exactly, as Haeckel figured them in some of his drawings "( emphasis in original ).

Haeckel and are
Haeckel, who admired Darwin's work, defined ecology in reference to the economy of nature, which has led some to question whether ecology and the economy of nature are synonymous.
Haeckel argues that certain features in embryonic development are conserved and palingenetic, while others are caenogenetic.
As Erland Nordenskiöld argues, charges of fraud against Haeckel are unnecessary.
In fact, ontogeny evolves – the phylogenetic history of a species cannot be read directly from its ontogeny, as Haeckel thought would be possible, but characters from ontogeny can be ( and have been ) used as data for phylogenetic analyses ; the more closely related two species are, the more apomorphies their embryos share.
In the case of echinoderms, he argued that the bilateral larvae must have been introduced after the establishment of the existing classes, and he challenged Haeckel s view that these larvae are evidence that echinoderms evolved from bilateral ancestors.
Baruch Spinoza, Gottfried Leibniz, Gustav Theodor Fechner, Friedrich Paulsen, Ernst Haeckel, Charles Strong, and partially William James are considered panpsychists.
One issue they highlighted was Wells ' accusation that Haeckel forged images of embryos that are allegedly still in biology books.
Ernst Haeckel claimed that Negroes have stronger and more freely movable toes than any other race which is evidence that Negroes are connected to apes because when apes stop climbing in trees they hold on to the trees with their toes, Haeckel compared Negroes to “ four-handed ” apes.
In modern biology ( e. g. Haeckel and Fritz Müller ), palingenesis has been used for the exact reproduction of ancestral features by inheritance, as opposed to kenogenesis, in which the inherited characteristics are modified by environment.

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