PAL'INGEN'ESIS (Neo-Lat.. from Gk. arci\Lv, polite, again fn°ntsis, birth). amt CCENOGENESIS. The reeapitulat ion theory (q.v.) or 'biogenetic law' is a statement of the general fact that the developmdmt of the individ ual is an epitome of that of the class tee which it belongs. Haeekel, and Fritz Midler in sub stance before him. further distilimlished two modes of operation of this law. To the first lie pave the name `palingenesis.' Briefly defined. it is the fact of the regular repetition of ancestral caused by inheritance. Thus the shrimps and erabs in the egg pass through a nauplius stare. the embryo possessing the rudiments of only three pairs of appendages. but they hateh in an advanced larval condition called the The lobster. on the other hand, before hatehing passes through phases which recall the nauplins, and also the zoi!a stages, and the animal hatches in a more advanced stage than the zoSa, under going a partial metamorphosis. The toad or frog. in the embryo, pass through an aseidian, an Amphioxus, a fish, and a salamander stage, before they assume the tailless adult condition.
The animal thus repeats in its own develoionent certain but not all) of the features which char acterized its successively ascidian, Amphioxus like, and lish-like ancestors.
The second phase or mode of operation of the law of recapitulation is 'etenogenesis,' which means the moditiention of palingenesis by the in heritance of later acquired characters, the ances tral eharacters having been lost or crowded out, owing to the lapse of heredity. This was fully
explained by Fritz Nutter, his illustration being the metamorphosis of the more specialized in sects, such as the butterfly. bee. and fly. The larval stages of these insects (caterpillar, mag got) are secondary. The most primitive insects were horn in the shape of the parent, and passed through no larval stage. The primitive features of the ancestral insect have been lost, except the transitory indications of a series of abdominal legs, showing that the insects all descended from polypodous forms; hut the eater pillar and mag-s got stages are recent acquisitions, and to this phenomenon the term camogenesis (or recent genesis) is applied. As Hillier expressed it: In contradistinetion to the inherited metamorphosis of the prawns, we may call that of the Coleop tern, Lepidoptera, etc., an acquired metamor phosis.. lie then goes on to show at some length that the 'complete' metamorphosis of insects was not inherited from the primitive ancestor of all insects, but acquired at a later period. See RECA PITULATION THEORY.
Consult: Fritz Miller, Facts for Darwin (Lon don, 1S69) ; Haeckel, Morphologic (Ber lin, 1866) ; Hyatt, Phyloyeny of an Acquired Character (Philadelphia. 18941: Lang, Text book of Comparative Anatomy, vol. i. (New York, 1891).