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.

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.

Haeckel ’ s embryo drawings are primarily intended to express his idiosyncratic theory of embryonic development, the Biogenetic Law, which in turn assumes ( but is not crucial to ) the evolutionary concept of common descent.

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 ’ s ‘ Biogenetic 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.

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.

The published artwork of Haeckel includes over 100 detailed, multi-colour illustrations of animals and sea creatures ( see: Kunstformen der Natur, " Art Forms of Nature ").

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.

German biologist Ernst Haeckel popularized medusae through his vivid illustrations, particularly in Kunstformen der Natur.

The underlying debate between Haeckel and His derives from differing viewpoints regarding the similarity or dissimilarity of vertebrate embryos.

" 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 ).

Although the early embryos of different species exhibit similarities, Haeckel apparently exaggerated these similarities in support of his Recapitulation theory, sometimes known as the Biogenetic Law or " Ontogeny recapitulates phylogeny ".

Haeckel proposes that all classes of vertebrates pass through an evolutionarily conserved “ phylotypic ” stage of development, a period of reduced phenotypic diversity among higher embryos.

His, in opposition to Haeckel, seeks to take human embryos out of the hands of Darwinist proponents.

His also accuses Haeckel of creating early human embryos that he conjured in his imagination rather than obtained through empirical observation.

Haeckel produced several embryo drawings that often overemphasized similarities between embryos of related species.

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.

One issue they highlighted was Wells ' accusation that Haeckel forged images of embryos that are allegedly still in biology books.

As a result of his letters and, no doubt, personal conversations, Huxley and Haeckel were convinced that, at the time he wrote Principles, he believed new species had arisen by natural methods.

In 1852, Haeckel completed studies at Cathedral High School ( Domgymnasium ) of Merseburg.

Haeckel studied under Karl Gegenbaur at the University of Jena for three years, earning a doctorate in zoology, before becoming a professor of comparative anatomy at the University of Jena, where he remained for 47 years, from 1862 to 1909.

From 1866 to 1867, Haeckel made an extended journey to the Canary Islands with Hermann Fol and during this period, met with Charles Darwin, in 1866 at Down House in Kent, Thomas Huxley and Charles Lyell.

Karl E. von Baer and Haeckel both struggled to model one of the most complex problems facing embryologists at the time: the arrangement of general and special characters during development in different species of animals.

In the latter 19th century, the department of zoology taught evolutionary theory, with Carl Gegenbaur, Ernst Haeckel and others publishing detailed theories at the time of Darwin's " Origin of Species " ( 1858 ).

" He sometimes retorted sharply, " I am sorry to have to inform you that I do not believe in the Bible as a divine revelation, & therefore not in Jesus Christ as the Son of God ", and at other times was more guarded, telling a young count studying with Haeckel that " Science has nothing to do with Christ ; except in so far as the habit of scientific research makes a man cautious in admitting evidence.

As a professor of anatomy at the University of Jena ( 1855 – 1873 ) and at the University of Heidelberg ( 1873 – 1903 ), Carl Gegenbaur was a strong supporter of Charles Darwin's theory of organic evolution, having taught and worked, beginning in 1858, with Ernst Haeckel, 8 years his junior.

In 1855, he was appointed extraordinary professor of anatomy at the University of Jena, and in 1858, he became the ordinary professor, where after 1865, his former student and fellow-worker Ernst Haeckel was professor of zoology.

In 1858, the physician Ernst Haeckel studied under Carl Gegenbaur at Jena, receiving a doctorate in zoology ( after his medical degree ), and became a professor at the same institution, the University of Jena ( see: Ernst Haeckel ).

Roux was a disciple of and influenced by Ernst Haeckel who believed the struggle for existence occurred at the cellular level.

His ideas changed in summer 1862 when he returned to study at Jena, where Ernst Haeckel introduced him to Darwin's work and theories.

Dohrn received his doctorate in 1865 at Breslau under Eduard Grube, and his Habilitation in 1868 at Jena with Rudolf Virchow, Ernst Haeckel and Carl Gegenbaur.

During these times, he worked several times at facilities located by the sea: Heligoland alongside Haeckel in 1865, Hamburg in 1866, Millport, Scotland with David Robertson in 1867 and 1868 and moved to Messina, Italy, during the winter of 1868 together with his friend and colleague Nicholas Miklouho-Maclay to work on the marine life of the Straits of Messina.

This contention may look convincing at first glance inasmuch as On the Origin of Species is full of observations and proposed mechanisms that clearly fit within the boundaries of modern ecology ( e. g. the cat-to-clover chain – an ecological cascade ) and because the term ecology was coined in 1866 by a strong proponent of Darwinism, Ernst Haeckel.

Darwin was visited in October 1866 by the zoologist Ernst Haeckel, who over the years had built support for Darwin in Germany, now getting huge classes at Jena for his lectures on Darwinismus.