Editing Ray Lankester (section)

=== Invertebrates and degeneration ===
Lankester's books ''Developmental history of the Mollusca'' (1875) and ''Degeneration: a chapter in Darwinism'' (1880) established him as a leader in the study of invertebrate life histories. In ''Degeneration'' he adapted some ideas of [[Ernst Haeckel]] and [[Anton Dohrn]] (the founder and first director of the [[Stazione Zoologica]], [[Naples]]).<ref>Dohrn, Anton 1875. ''Der Ursprung der Wirbelthiere und das Principe des Functionswechsels''. Engelmann, Leipzig.</ref> Connecting Dohrn's work with [[Darwinism]], Lankester held that degeneration was one of three general avenues that evolution might take (the others being balance and elaboration). Degeneration was a suppression of form, "Any new set of conditions occurring to an animal which render its food and safety very easily attained, seem to lead to as a rule to Degeneration".<ref>[https://www.biodiversitylibrary.org/item/23841#page/45/mode/1up Lankester, E. Ray (1880) ''Degeneration: a chapter in Darwinism'', p. 33].</ref> Degeneration was well known in parasites, and Lankester gave several examples. In ''[[Sacculina]]'', a genus of [[barnacles]] which is a parasite of [[crab]]s, the female is little more than "a sac of eggs, and absorbed nourishment from the juices of its host by root-like processes" (+ [[Wood engraving|wood-engraved]] illustration). He called this degenerative evolutionary process in parasites ''retrogressive metamorphosis''.

Lankester pointed out that retrograde metamorphosis could be seen in many species that were not, strictly speaking, degenerate. "Were it not for the recapitulative phases of the [[barnacle]], we may doubt whether naturalists would ''ever'' have guessed it was a [[crustacean]]." The lizard ''[[Tetradactylus|Seps]]'' has limbs which are "ridiculously small", and ''[[Bipes (lizard)|Bipes]]'', a burrowing lizard, has no front limbs, and rear limbs reduced to stumps. The [[Dibamidae]] are legless lizards of tropical forests who also adopt the burrowing habit. [[Snakes#Evolution|Snakes]], which have evolved unique forms of [[Snakes#Locomotion|locomotion]], and are probably derived from lizards. Thus degeneration or retrogressive metamorphosis sometimes occurs as species [[Adaptation|adapt]] to changes in [[Habit (biology)|habit]] or way of life.

As evidence of degeneration, Lankester identifies the recapitulative development of the individual. This is the idea propagated by [[Ernst Haeckel]] as a source of evolutionary evidence ([[recapitulation theory]]). As antecedents of degeneration, Lankester lists:<ref>Lankester, E. Ray (1880) ''Degeneration: a chapter in Darwinism'', p. 52.</ref>
:1. [[Parasitism]]
:2. Fixity or immobility ([[Sessility (zoology)|sessile]] habit)
:3. Vegetative nutrition
:4. Excessive reduction in size
He also considered the [[axolotl]], a [[mole salamander]], which can breed whilst still in its gilled larval form without maturing into a terrestrial adult. Lankester noted that this process could take the subsequent evolution of the race into a totally different and otherwise improbable direction.<ref>[[#Lester|Lester]], p. 87.</ref> This idea, which Lankester called ''super-larvation'', is now called [[neoteny]].

Lankester extended the idea of degeneration to human societies, which carries little significance today, but it is a good example of a biological concept invading social science. Lankester and [[H. G. Wells]] used the idea as a basis for propaganda in favour of social and educational reform.<ref>{{Cite journal
 | pmid = 16769556
| year = 2006
| last1 = Barnett
| first1 = R
| title = Education or degeneration: E. Ray Lankester, H. G. Wells and the outline of history
| journal = Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences
| volume = 37
| issue = 2
| pages = 203–29
| doi = 10.1016/j.shpsc.2006.03.002
}}</ref>