Fertilisation , Apogamy and Parthenogenesis. 157 
polar-cells is formed by the division of the first one into two 1 and, 
the three cells are not extruded but merely lie in the periphery of 
the egg. The second polar-cell then fuses with one of the products 
of division of the first and thus produces a nucleus with the normal, 
somatic number of chromosomes. This cell then undergoes a 
number of divisions and migrating into the body of the developing 
embryo forms there the genital gland. If these observations be 
correct, and there seems little reason to doubt there accuracy, the 
body of the drone is clearly of composite nature, the ordinary 
somatic cells being truly parthenogenetic in origin, while the genital 
gland is derived from an endogamous fusion of gametes of the 
relationship of cousins. 
Observation such as these in Apis; the fusion of the sister 
nuclei in Artemia; the special methods to prevent reduction to 
be observed in animals and plants in the peculiar cases (usually 
termed parthenogenesis) in which a special cell is produced which 
develops like an egg-cell without fertilisation ; the absence of evidence 
in plants, and the doubtful evidence in animals, 1 of the capacity 
of normal eggs with the reduced number of chromosomes to produce 
complete mature individuals in a parthenogenetic way; all suggest 
the importance to the organism of starting its life history with a 
complete (unreduced) nuclear mechanism. Though the chromo¬ 
somes appear to be doubled again in the drone-egg, yet this does 
not seem to be sufficient for complete development, for the sexual 
cells are derived in another way. 2 
Such fusions of nuclei as are to be observed in the egg of the 
honey-bee and in that of Artemia cannot be conceived as either 
bringing about mingling of different characters or producing any 
stimulus to further development; they must be considered as types 
of reduced fertilisation which have for their purpose the mere 
provision of a complete nuclear mechanism, i.e. the doubling of the 
number of chromosomes. It seems then permissible to doubt whether 
such reduced forms of fertilisation as are to be observed in the 
1 The doubtful nature of true parthenogenesis in animals is also 
recognized by Phillips (A Review of Parthenogenesis. Contrib. 
Zool. Lab. Univ. Pennsyl. X. (1903), p. 275. 
2 Delage states that even in artificial parthenogenesis and in 
mcrogony (the development of portions of egg cytoplasm 
which have been fertilised by spermatozoa) the full number of 
chromosomes may be restored in some vegetative way. 
There seems some doubt about this point and these results 
are certainly contrary to those obtained by Morgan on 
merogony, and by Wilson on the artificial parthenogenesis of 
the eggs of Toxopneustes. In no case, has a mature individual 
been obtained in this way. 
