On Reproduction, Animal Life Cycles. 89 
led to the discussion as to the genetic significance of this compound 
organization. These are illustrations where the metagenesis has be- 
come to some extent secondarily suppressed. 
But because the separation of individuals may not be very apparent 
in no way speaks against the occurrence of metagenesis, provided 
there are acts of budding or fission alternating with generation by 
eggs; this is the cardinal criterion. From a certain area of the 
Echinoderm larva the adult arises as a virtual bud; and in some 
species, as Johannes Mueller long ago discovered, the embryonic star- 
fish may early separate from the larva, and the latter continue an 
independent existence for some time. Here there can be no question 
that the larva is a first individual that produces a second by budding. 
It is but a step from this to the case of the Nemertines: from four 
particular points of ectoblast of the' Pilidium larva the adult body 
takes its origin; these points comprise only a small areal extent of 
the larva; and though in this case the larva does not continue to live 
after the formation of the worm embryo, it is nevertheless a first 
individual that generates a second by budding. 
Few can hesitate to acknowledge the preceding to be cases of meta- 
genesis. But, as Beard 22 has reasoned, the same should be concluded 
for a great variety of other cases that are generally not considered 
metagenetic. An Echinoderm larva that dies during the formation 
of the embryo, does not continue a separate existence, is also a case 
of metagenesis; for it is but a step from this example to the one 
previously mentioned. Among insects with a more or less complete 
metamorphosis the crawling larva becomes a quiescent pupa; then 
from a series of points of the hypodermis of the pupa the organs of 
the imago are formed, while all the remaining tissues of the pupa 
degenerate by histolysis and then become ingested by phagocytes. 
Therefore an adult Fly or Moth or Wasp is an individual quite dif- 
ferent from the pupa, an individual produced asexually by the con- 
junction of a series of buds. This is in every sense as truly metagene- 
tic as the development of a medusa from a polyp. Further, the 
recent studies of Woltereck 23 on the trochophore larvae of Annel- 
dids show that the adult grows merely from an anterior and a pos- 
terior end of the larva, while the large and complex intermediate zone 
of the larva gives rise to no organs of the adult but dies down and 
is later discarded. Here is true metagenesis in Annelids: the adult 
is formed through budding by a larva. Yet how slow we have been 
to recognize these examples and similar ones as metagenetic! 
In fact whenever in development there is discontinuity of process 
22 0n a Supposed Law of Metazoan Development, 1893, Anat. Anz., 8. 
23 Trochophora-Studien, 1902, Stuttgart. 
