April,1919 Bulletin of the Brooklyn Entomological Saciety. 37 
tion with the profound chemical changes in the blood, etc., which 
occur at the approach of this period. These matters, however, 
deal with the physiological rather than the “phylogenetic” ex- 
planation of the phenomena of metamorphosis. 
Quatrefages (Métamorphoses de l’Homme et des Animaux, 
p- 133) states that “la larve n’est qu’un embryon a vie indépen- 
dante,” and as Lameere says (Ann. Soc. Ent. Belgique, Vol. 43, 
1899, p. 624) : “a la suite d’Owen, et cette interprétation se trouve 
encore répétée dans des traités de Zoologie tres récents, on a con- 
_sidéré que ce phénoméne (metamorphosis) était la manifestation 
d'une dilatation embryogénique ; l’évolution des Inséctes a méta- 
morphoses completes se ferait en dehors de l’ceuf, la larve serait 
un embryon vivant a découvert, tandis que les autres Insectes 
subiraient les mémes métamorphoses dans Vceuf. Avebury 
(Origin and Metamorphoses of Insects, 1902, p. 80) comes to 
the following conclusions: “‘ That the occurrence of metamorpho- 
sis arises from the immaturity of the condition in which some 
animals quit the egg. That the form of the insect larva depends 
in great measure on the conditions in which it lives. The exter- 
nal forces acting upon it are different from those which affect 
the mature form; and thus changes are produced in the young, 
having reference to its immediate wants rather than to its final 
form.” He therefore divides metamorphoses into “ develop- 
mental and adaptive” types. He also states that the abruptness 
of the changes undergone by insects is due in great measure to 
“the hardness of their skin, which admits of no gradual altera- 
tion of form,” and suggests that “the immobility of the pupa or 
chrysalis depends on the rapidity of the changes going on in it.” 
If the larval stages of insects with complete metamorphosis 
represent, so to speak, “free-living embryos,’ while similar 
changes supposedly undergone within the egg by insects which 
do not exhibit such a metamorphosis, embryology should give 
some basis for such an assumption—which, however, is not the 
case. Furthermore, insects leaving the egg in an earlier stage of 
development (as those with complete metamorphosis are sup- 
posed to do) should be more primitive than those remaining for 
a longer period of development within the egg (as the non- 
metabolous forms are supposed to do), somewhat after the 
