Br.) 
ee 
559 
and the female-eges, is needful. The germ-cells of the female thus 
make provision not only for a new batch of female-eggs but also for 
one of male-eggs. On the other hand, the germ-cells of the male 
only furnish one form of functional gamete. The deter- 
mination of sex for the next generation thus lies with 
the germ-cells ofthefemale metazoan organism. 
Under the generally accepted but erroneous view of the existence 
of only two forms of gametes, eggs and “ordinary” spermatozoa, in 
the Metazoa but one form of individual can arise. Ordinary herm- 
aphroditism illustrates the truth of this, for here all the individuals 
arising from the union of such germ-cells are alike. For the constant 
production of two forms of individuals three categories of gametes at 
least are needed. 
In all dioecious Metazoa three kinds of functional gametes 
are constantly required and differentiated, of these two arise in the 
female, one in the male. 
Dioecious and hermaphrodite Metazoa may be defined as 
animalforms, in whichinevery sexualindividual either 
two categories of gametes, or the forerunners of such, 
are constantly differentiated. Of these gametes never more 
than three sorts are functional (dioecious forms), and there may be 
but two such (some hermaphrodites). 
The actual determination of sex is initiated at the division of 
the primary germ-cells into secondary ones: it is completed at the 
formation of the oöcytes and spermatocytes, and its manifestation 
is accomplished by the numerical reduction of the 
chromosomes inthese. 
While to all appearance the determination of sex would be effected 
in plants at the formation of the spore-mother-cells'), it does not 
come about in their equivalents in animals, the primary germ-cells; 
for if one of these undergo independent development alongside the 
embryo, the result is the bringing-forth of like twins. All known cases 
of such are of the same sex, and from this it would follow, that all 
the primary germ-cells of a given case are alike in sexual potential- 
ities as in other respects. All the evidences go to prove, that the 
determination of sex does not take place later than the formation of 
the oöcytes and spermatocytes. The history of the two sorts of 
eggs of Hydatina senta, Dinophilus gyrociliatus, Phylloxera, and Raja 
1) A view apparently also held by Srrassureur (Biol. Centralbl., 
ibd. 20, 1900, p. 769). 
