Antithetic Alternation of Generations . 447 
becomes absolutely essential to itj? being carried out. A priori 
it seemed quite hopeless to expect that our knowledge of 
the processes of conjugation in the Infusoria, which we owe 
so largely to the brilliant labours of Richard Hertwig and 
E. Maupas, would confirm the suspicion that existed of the 
occurrence of a spore-formation with reduction of the number 
of chromosomes after a conjugation or antecedent to a new 
one in this group, but, as will subsequently appear, the known 
facts readily allow of such an interpretation. 
1 1 % 
