278 CLA YPOLE. [Vou. XIV. 
(10) The embryo appears encircling the egg as a narrow 
girdle, stopping each side of the precephalic organ. 
(11) An extra pair of mouth-parts appears, forming in the 
adult two lateral folds inclosing the mouth-parts. This is 
homologous with the second pair of crustacean antennae. 
(12) Yolk is included in the reproductive organs and lies free 
in the body cavity, but is not found in the mesenteron. 
(13) Anurida shows characters allying it with crustaceans 
and myriapods rather than the rest of the Insecta. 
In consideration of all these points it is clear that Anurida 
possesses certain characters allying it closely to the lower 
arthropod groups. The holoblastic cleavage and egg mem- 
branes ally it to both crustaceans and myriapods, while the 
structure of the ovary is most like the synthetic type Scolo- 
pendrella, but more like the chilognath myriapod than the 
chilopod. In spite of the possession of some generalized 
characters, it is evident that Anurida is a degenerate type that 
has been developed by a lengthening of embryonic life and a 
shortening of adult life. Paedogenesis, the sexual maturing of 
a larva, is illustrated by this process. The absorption of the 
embryonic yolk by the reproductive organs and the great maturity 
of the products even immediately after hatching both point to 
a tendency to shorten adult life and to omit larval development 
even to the extent of assuming the larval form for the adult. 
The decrease in the number of abdominal segments is only 
another step in the same direction. If the insect may be con- 
sidered a larval chilognath sexually matured and bearing the 
three pairs of legs found in the chilognath larva, so can an 
Anurida be considered a very simple insect embryo matured 
sexually. Observations have been before advanced to estab- 
lish the progressive shortening in some forms and gradual 
elimination of larval forms. 
Anurida shows additional interesting points. By its curious 
habitat, chiefly under water, it has lost the need for tracheae, 
and, consequently, they are so far obliterated as to be absent 
even in the embryo; its respiration is purely cutaneous. It has 
been remarked that the amnion and serosa, the cellular envel- 
