THE SPERMATOPHORE IN ARENICOLA 1023 
THE ALTERNATION OF GENERATIONS 
There follows the union of the sperm and the egg, the second 
individual in the alternation, what we ordinarily know as the 
adult worm. This individual it is that produces the spermato- 
gonia or oogonia, or in other words, the asexual spores. 
Botanic use of the term 
The conception of the alternation of generations has developed 
in its clear-cut simplicity among the botanists. It is that in the 
life history of a form there are two generations, one of which pro- 
duces sexually, the other by asexual spores. It is typified in the 
bryophytes and most pteridophytes. In the higher plants the 
sexual or gametophyte generation is gradually reduced so that it 
is only in relatively recent times that its existence as such has been 
recognized in the phaenogams. 
Usual zoological significance 
The term alternation of generations has been used by zoolo- 
gists in a totally different sense. Two generations occur in many 
animals, the so-called sexual and asexual. The latter originates 
from a fertilized egg; the former arises by budding or a similar 
process from the asexual generation. There is thus an alterna- 
tion of a generation that reproduces sexually with one that is 
never sexual, but the latter does not reproduce by asexual spores 
as is the case in plants. It is unfortunate that the same term 
is used for both processes. The asexual generation in the animal 
alternation is much more comparable to the sporophyte which is 
produced in propagation by cuttings or by runners. I am using 
the term alternation of generations strictly as it is understood 
by botanists. 
ALTERNATION OF GENERATIONS AND REDUCTION 
Now in all except the lowly plants, in all the archegoniates and 
even in many algae this alternation of generations is accompanied 
by the phenomenon of chromatin reduction, and reduction seems 
