986 The American Naturalist. [October, 
"Conjugation in the Infusoria.°—Lack of material has hitherto 
been the chief difficulty in the way of thorough study of the phenomena 
of conjugation. Investigators like Balbiani, Stein, and Biitschli have 
complained of the rarity of this state, and have explained their incom- 
plete and fragmentary observations on this ground. The subject itself 
is extremely complex, and requires, as a first condition of successful 
study, most abundant material. 
Thanks to Maupas, we now know how to supply this need. Take 
stagnant water containing algze, conferve, debris of dead leaves, and 
other vegetable matter, and keep it in dishes covered with glass plates, 
to prevent evaporation and to guard against dust, until putrid fermen- 
tation sets in. Infusoria contained in this water, finding abundant 
nourishment, multiply in great numbers. When they become abun- 
dant they may be taken up in a drop of water and kept on slides in 
damp chambers, as before described.” The infusoria continue to mul- 
tiply until the supply of. food fails; hunger then leads them to con- 
7ugate. 
_ When rare species are desired, which do not multiply rapidly in 
small aquaria, two individuals from different sources may be isolated, 
and made to multiply on slides kept in damp chambers. Mixture of 
specimens from the two slides, when the food-supply is exhausted, 
usually results in conjugations, 
The isolation of groups of infusoria on slides offers still another 
important advantage: it enables one to examine them easily with the 
microscope, and thus to catch the first conjugations. 
upas calls attention to the fact that, as a general rule, conjugation 
is most frequent towards the end of nightand during the early morning 
hours. 
In beginning the study of a new species the first thing to determine 
is the duration of the period of conjugation. This point ascertained 
wil serve to guide the course of investigation. The isolation of 
couples in conjugation is indispensable to the study of the phenomena 
following separation. 
For killing isolated couples at successive hours, in order to trace the 
history of the nuclei, Maupas recommends corrosive sublimate (1: 100) 
as the best reagent. He proceeds as follows: The infusoria are taken 
up with a pipette and placed in a drop of.water on a slide. Fine 
hairs, suited in thickness to the species under study, are then placed 
on either side of the drop, as supports for the cover-glass. The in- 
ê Maupas. Arch. de Zool. exp. et gén., 1889, No. 2, p. 168. 
1 NATURALIST, April, 1889. 
