2 t 2 Alternation of Generations and Ontogeny. 
antherozoids, and diploid (so-called parthenogenetic) eggs are of 
course known in angiosperms also. In animals, haploid, male 
individuals which produce normal (haploid) spermatozoa are known 
in the normal life-history of bees and hornets. Delage also has 
lately succeeded in rearing to a sexual condition a haploid echinoderm 
produced from a fertilised non-nucleate egg-fragment. It is true that 
spores have not yet been produced on a haploid sporophyte, but in 
face of the evidence from animals (that germ-cells which usually 
arise from diploid can develop from haploid cells) it cannot be 
considered an impossibility . 1 
Both general considerations and actual evidence clearly show 
that the assumption of the relation of cytological character and the 
two types of reproduction is not warranted. What is definitely 
associated with difference of chromosome number is, of course, the 
regular succession of the processes of fertilization and reduction; 
these two processes are never known to occur in the absence of 
cytological differences 2 though the reproductive organs usually 
associated with these processes may still be produced . 2 
We seem then to be driven to the view that even in Dictyota 
the germ cells have not similar morphogenetic properties but that 
the egg is set free with a tendency impressed upon it, which keeps 
latent the determinants relating to the sexual organs, while the 
spore has a tendency which keeps the tetrasporangial characters 
latent. In other words Dictyota shows a cyclic correlation, in which 
one phase of the life-cycle brings on the other. 
Although there is clear evidence in the case of the Uredineae 
of differentiation of germ-cells (apart from cytological characters) 
according to their position in the life-cycle, and very strong evidence 
for the same in Dictyota, the most striking case would be one in 
which we had an organism with two somatically distinct generations 
which start life under similar conditions. Such a case we appear to 
have among animals in the Foraminifera. These are aquatic Protozoa, 
mostly marine, many of which exhibit a well-marked dimorphism, 
which may be so distinctly marked that the two forms have been 
1 Possibly Yamanouchi’s artificiality induced haploid sporophyte 
of Nephrodium molle (Bot. Gaz. XLIV., 1907, p. 145) will be found 
to produce the required stage. 
2 Reduction in haploid cells is hardly conceivable, but it is possible 
that the diploid eggs obtained in Bryophyta by E. & E. Marchal 
(Bull, de l’Acad. Roy. de Belgique. Classe des Sciences, 
1907, p. 788) and also those of ferns, might be fertilized, when 
we should have tetraploid cells (which are said to arise in 
another way in Poly trichum). If such forms could be reared 
their later behaviour would be of great interest. 
