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JOURNAL OF THE PLYMOUTH INSTITUTION. 
the field of the microscope, and from the constant vibration of 
their cilia, they were very troublesome, at least up to the time when 
the Doctor had directly observed their friendly co-operation in the 
fertilization he was studying. Numerous antherozoids were whirled 
round and round in the whirl caused by a vorticellae, and frequently 
antherozoids came into contact with the trichogyne and remained 
attached to it for a longer or shorter period. It was entirely due 
to the motion caused by vorticellae that Dr. Dodel-Port was enabled 
to follow the phenomena of the attachment of the antherozoids to 
the trichogyne from beginning to end. The motions of the vorti- 
cellae 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 passive body that may be suspended in the 
water. The presence of numerous vorticellae thus imparts to the 
passive antherozoids a kind of motion much resembling that of the 
sperm cells of other cryptogams which are endowed with active 
cilia. From this it follows with mathematical certainty that the 
probability of the antherozoid falling on the trichogyne in the 
presence of vorticellae is immensely greater than that which would 
exist were there no animals present. 
At present we have but a short account of this discovery, which 
has just appeared in Nature, translated from Kosmos, from which 
I have quoted, and further particulars are awaited with interest. 
Dr. Dodel-Port, in conclusion, says, " The total absence of active 
organs of locomotion in the antherozoids of Florideae points to a 
common ancestor from which the different branches of the Florideae 
have inherited the immobility of the antherozoids. No doubt that 
during the differentiation of the red seaweeds, many forms have died 
out in consequence of the fertilization not taking place through the 
passivity of the male cells, while other forms have retired to 
localities which, through active water currents, favour the process 
of fertilization in spite of the immobility of the antherozoids. It 
is well known that now we find most of the present species of the 
Florideae on the coasts of warmer seas, which are constantly washed 
by the waves, while the northern coasts, which are covered by 
crusts of ice during a great portion of the year, are very poor in 
red seaweeds. Future researches will have to show how far in 
many of these aquatic plants the differentiation of the genera took 
place, in the sense of an adaptation to the small marine animals 
