400 THE ZOOLOGIS'r. 
animalcules, Vorticelle, which had settled there, and were as usual 
in incessant motion. Often they appeared in dozens in the field 
of the microscope, and with the constant vibration of their cilia 
were very troublesome, until Dr. Dodel-Port discovered their 
friendly co-operation in the fertilisation he was studying. He 
was a frequent witness of the process depicted in Fig. 3, where 
numerous antherozoids were whirled round and round in the 
whirl produced by a Vorticella, and where antherozoids frequently 
came in contact with the trichogynium, and remained attached to 
it (Fig. 8, s’ and s”) for a longer or shorter period. It was 
entirely due to the motion caused by Vorticelle that Dr. Dodel- 
Port was enabled to follow the phenomenon of the attachment — 
of the antherozoids to the trichogynium from beginning to 
end. The motions of the Vorticelle are particularly varied 
through the repeated contractions of their stalks into short 
spirals, and thus they cause various currents in the water, by all 
of which the antherozoids are carried along, like any other small 
and passive body that may be suspended in the water. (Compare 
Fig. 2, where one of the Vorticelle is just contracting its stalk, 
the arrows in each case indicating the direction of the currents.) 
The presence of numerous Vorticelle thus imparts to the passive 
antherozoids a kind of motion much resembling that of the 
