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It places itself upon the surface of the animal on which it feeds, and, if it have any hard parts, it simply sucks the juices, dropping the dead carcass immediately after; but it swallows whole the little Acalephs of other Species and other soft animals that come in its way. Early in summer these Jelly-Fishes drop their eggs, little transparent pear-shaped bodies, covered with vibratile cilia.
In the first place, what is that characteristic motion which it so constantly assumes that restless swinging from side to side? Is it a property inherent in its own nature, or is it a power communicated to it from without? There is a train of wheelwork enclosed with it in the case. Is that the source of its vibratile mobility? Assuredly not.
They may be seen in great numbers in the spring, floating about in the water, or rather swimming, for the motion of all Radiates in their earliest stage of existence is rapid and constant, in consequence of the vibratile cilia that cover the surface.
Within these lobules the spermatozoa are formed by a complex process of cell division and cell germination upon whose description we need not enter here. The spermatozoon may be described as the male sexual cell whose function is to fertilize the female ovum. The spermatozoon is about 1/20 of an inch in length and consists of a head, body and a vibratile tail.
Each of these processes is capable of striking water like an oar; and the consequence is that the young creature is propelled through the water. So that you have the young polype floating about in this fashion, covered by its 'vibratile cilia', as these long filaments, which are capable of vibration are termed.
The protoplasm of Algae and Fungi becomes, under many circumstances, partially, or completely, freed from its woody case, and exhibits movements of its whole mass, or is propelled by the contractility of one, or more, hair-like prolongations of its body, which are called vibratile cilia.
Fit the same intellect to a man and it is a bow- string, to a woman and it is a harp-string. She is vibratile and resonant all over, so she stirs with slighter musical tremblings of the air about her. Ah, me! said my friend, the Poet, to me, the other day, what color would it not have given to my thoughts, and what thrice-washed whiteness to my words, had I been fed on women's praises!
In all its structure it tells us of something earlier and far simpler, but what this earlier ancestor was we do not know. Rather more highly organized relatives of the amoeba, the flagellata, have produced a membrane, and swim by means of vibratile, whiplash-like flagella.
On coition, the semen being received into the female organs, which are at that time in a state of turgescence, the spermatozoa, by means of their own vibratile activity, find their way into the Fallopian tubes, and here come in contact with the ovule. The ovule is a minute cell with a transparent membrane, within which is the yolk containing the germinal vesicle.
Such an animal soon completes its growth: for the stage which I have spoken of as transient for the higher Radiates is permanent for these; and when the little sphere moving about by means of its vibratile cilia has elongated a little, attached itself by the lower end to some surface, while the inversion of the upper end has formed the mouth and digestive cavity, and the expansion of its margin has made the tentacles, the very simple story of the fresh-water Hydra is told.
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