Editing Embryo drawing (section)

===Karl Ernst von Baer (1792–1876)===
Haeckel was not the only one to create a series of drawings representing embryonic development.  [[Karl Ernst von Baer|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 relation to developmental timing, von Baer's scheme of development differs from Haeckel's scheme.  Von Baer's scheme of development need not be tied to developmental stages defined by particular characters, where recapitulation involves [[heterochrony]].  Heterochrony represents a gradual alteration in the original phylogenetic sequence due to embryonic adaptation.<ref>Richardson, Michael K. and Gerhard Keuck, "Haeckel's ABC of Evolution and Development," p. 506</ref>
As well, von Baer early noted that embryos of different species could not be easily distinguished from one another as in adults.

[[Karl Ernst von Baer#Baer's laws|Von Baer's laws]] governing embryonic development are specific rejections of recapitulation.<ref name="Keuck p. 506"/> As a response to Haeckel's theory of recapitulation, von Baer enunciates his most notorious laws of development.  Von Baer's laws state that general features of animals appear earlier in the embryo than special features, where less general features stem from the most general, each embryo of a species departs more and more from a predetermined passage through the stages of other animals, and there is never a complete morphological similarity between an embryo and a lower adult.<ref>Gould, ''Ontogeny and Phylogeny'', p. 56</ref> Von Baer's embryo drawings<ref>{{cite web|url=http://www.sites.hps.cam.ac.uk/visibleembryos/s3_1.html|title=Histories of development|series=Making Visible Embryos}}</ref><ref>{{cite journal|author1=Erki Tammiksaar |author2=Sabine Brauckmann |volume=26|number=3/4|journal=History and Philosophy of the Life Sciences
|title=Karl Ernst von Baer's 'Über Entwickelungsgeschichte der Thiere II' and its Unpublished Drawings|year=2004|pages=291–308, 471–474|jstor=23333718|pmid=16302690}}</ref> display that individual development proceeds from general features of the developing embryo in early stages through differentiation into special features specific to the species, establishing that linear evolution could not occur.<ref>Richards, ''The Meaning of Evolution'', pp. 57–59</ref> Embryological development, in von Baer's mind, is a process of differentiation, "a movement from the more [[wikt:homogeneous|homogeneous]] and universal to the more [[heterogeneous]] and individual."<ref>Richards, ''The Meaning of Evolution'', pp. 59–60</ref>

Von Baer argues that embryos will resemble each other before attaining characteristics differentiating them as part of a specific [[family (biology)|family]], [[genus]] or [[species]], but embryos are not the same as the final forms of lower organisms.