894 The American Naturalist. [October, 
a period of pupal rest and non-nutrition, a rapid development 
to the mature stage takes place. Adventitious organs, useful 
to the larva, often develop, and are discarded in the pupal 
stage, as having no place in the phylogenetic order of develop- 
ment. This isstrikingly the case in Echinoderm development, 
the adventitious organs sometimes forming so large a part of 
the larval animal that they have the power of swimming and 
taking food after being discarded, though incapable of digest- 
ing it. In this case, the developing portion of the animal is 
confined to the central life organs. In other instances, the 
adventitious organs are absorbed and utilized in the process of 
change. ; 
As an instance of marked retention of the larval conditions, 
may be mentioned the Aphis, in which no further develop- 
ment takes place through many generations, nutrition being 
active, and reproduction going on by gemmation. In the 
autumn, when nutriment begins to fail, the long repressed in- 
stincts and developmental powers come into play, and mature 
insects are produced. The seventeen-year Cicadæ furnish anoth- 
er striking example,they continuing as larve during a very long 
period of underground nutrition, and developing to maturity 
only when unfolding instinct induces them to seek the surface. 
Numerous examples of a similar kind may be found in the 
Hydrozoa, in which development is checked at several larval 
stages, in each of which a different environment or kind of 
activity exists. 
The ants and bees, among insects, are of high interest in 
this inquiry. The bees, for example, seem to have worked out 
the whole problem for themselves, and can produce workers, 
queens and drones at will. It seems a simple question of 
nutrition whether queens or workers shall appear, the worker 
larvæ being underfed, the queen richly fed and with fuller 
space for growth. They all pass through stages of pupal de- 
velopment, in a state of rest and non-nutrition, but the fully- 
fed larva becomes a mature female, the illy-fed ones become 
immature females. During the subsequent life of the latter, 
no opportunity for complete development occurs, activity and 
nutrition being incessant. In the ants, somewhat similar con- 
ditions exist. 
