GERM CELLS IN THE ARTHROPODA 161 
Polyembryony has been described in an earthworm. 
Lumbricus trapezoides (Kleinenberg, 1879), in cer- 
tain Bryozoa (Harmer, 1893; Robertson, 1903), 
in the armadillo (Patterson, 1913), and in parasitic 
Hymenoprera (Marchal, 1904; Silvestri, 1906, 
1908). In every case cleavage is of the indeterminate 
type, and the cell lineage is unknown. Various 
theories have been advanced to account for poly- 
embryony, such as (1) blastotomy or the early 
separation of blastomeres, each giving rise to a 
single individual as has been brought about by 
Driesch (1892) and others by separating the blas- 
tomeres of the eggs of certain animals ; (2) polyovular 
follicles may occur in mammals and by some (Rosner, 
1901) are considered sufficient to account for poly- 
embryony among the members of this class; and 
(3) precocious budding has been suggested to account 
for the production of many individuals from a 
single egg, most recently by Patterson (1913), 
who has shown that in the armadillo the blastoderm 
produces two primary buds from each of which two 
secondary buds arise, and hence four young develop 
from each egg. According to the theory of germinal 
continuity each of the buds must be supplied with 
germ cells or with germ-plasm which has not yet 
been segregated into germ cells. Silvestri’s in- 
vestigations seem to indicate that the former is 
true for parasitic HymEnoprera, but it is difficult 
to see how a definite number of germ cells can be 
supplied to each bud during a process of development 
which is apparently so indeterminate. If, however, a 
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