United States or Rwanda ? Vote for the TOP Country of the Week !
Among protophytes it needs but to think of the multitudinous varieties of diatoms and desmids, with their elaborately-constructed coverings; or of the definite methods of growth and multiplication among such simple Algæ as the Conjugatæ; to see that most of their distinctive characters are due to inherited constitutions, which have been slowly moulded by survival of the fittest to this or that mode of life.
The same tendency is met with again at a higher stage, in the protophytes, which, once having quitted the parent cell by way of division, remain united to each other by the gelatinous substance that surrounds them also in those protozoa which begin by mingling their pseudopodia and end by welding themselves together. The "colonial" theory of the genesis of higher organisms is well known.
Protophytes. : 2. Algaria. Unicellular algae. : 2. Paulotomea. Palmellacea. Eremosphaera. 3 to 5. Protozoa. : 3. Lobosa. Amoebina. Amoeba Leucocyta. 3 to 5. Protozoa. : 4. Infusoria. Unicellular. : 4. Flagellata. Euflagellata. Zoomonades. 3 to 5. Protozoa. : 5. Blastaeades. Multicellular hollow spheres. : 5. Catallacta. Magosphaera, Volvocina, Blastula. 6 to 8.
Supposing the multitudinous specialities of the envelope in different orders and genera of protophytes to be set against one another, and mutually cancelled, there remains as a trait common to them an envelope unlike that which it envelopes.
Among plants, those of the Volvox type show us the component protophytes so feebly combined that they severally carry on their lives with no appreciable subordination to the life of the group. And among animals, a parallel relation between the lives of the units and the life of the group is shown us in Uroglena and Syncrypta.
When, by the decay of such protophytes, and that decomposition of rock effected by them, there had resulted a fit habitat for mosses; these, of which the germs might be conveyed in drifted trees, would begin to spread.
Why this marvellous fact? Meaning is given to it if we go back to the first stage in which Protozoa, having by repeated fissions formed a cluster, then arranged themselves into a hollow sphere, as do the protophytes forming a Volvox.
To disentangle such parts of their developmental changes as are due to the action of the medium, is therefore hardly possible. We can hope only to get a general conception of it by contemplating the totality of the facts. The first cardinal fact is that all protophytes are cellular all show us this contrast between outside and inside.
Word Of The Day