The parasites multiply in two ways - (a) by binary fission, and (b) by multiple division or segmentation.
(2) Autotomy, sometimes termed transverse fission, is the name given to a process of unequal fission in which a portion of the body separates off with subsequent regeneration.
A, Ordinary forms of varying sizes; b c, stages in multiple division; d, binary fission; e, f, g, flagellate forms (after Rogers).
In some Syllids this posterior region separates off from the rest, producing a new head; thus a process of fission occurs which has been termed schizogamy.
All Trypanosomes are capable of binary longitudinal fission, and this appears to be the chief method of multiplication.
B, a specimen undergoing fission (X 20).
Sooner or later, however, the scyphistoma produces free medusae by a process of transverse fission termed strobilization.
- Stages in Binary Longitudinal Fission of Trypanosoma brucei.
This theory of the genesis of double-stars by fission is not, however, universally accepted; in particular objections have been urged by T.
In this way we may distinguish, first, vegetative reproduction, the result of discontinuous growth of the tissues and cell-layers of the body as a whole, leading to (I) fission, (2) autotomy, or (3) vegetative budding; secondly, germinal reproduction, the result of the reproductive activity of the archaeocytes or germinal tissue.
The ovicells are modified zooecia, and contain numerous embryos which in the cases so far investigated arise by fission of a primary embryo developed from an egg.
In the Phylactolaemata, however, a new colony may originate not only from a larva, but also from a peculiar form of bud known as a statoblast, or by the fission of a fully-developed colony.
In the Cyclostomata the primary embryo undergoes repeated fission without developing definite organs, and each of the numerous pieces so formed becomes a free larva, which possesses no alimentary canal.
Equiperdum) the longitudinal fission is apparently multiple, three or even four descendants being produced simultaneously.
These young individuals can themselves multiply by equal binary fission, giving Anterior flagellum; Posterior flagellum; Longitudinal striations nemes); Cytoplasmic vacuole.
Diagram of transverse fission 7.
(I) True fission or longitudinal division of an individual into two equal and similar daughter-individuals is not common but occurs in Gastroblasta, where it has been described in detail by Arnold Lang .
A " stolon " of unknown origin produces thirty-two buds, which become as many Polypodia; each has twenty-four tentacles and divides by fission repeated twice into four individuals, each with six tentacles.
Under these conditions the lactose decomposes into dark-brown fission products, the fat loses its emulsified condition and separates out as cream which cannot be made to diffuse again even by shaking, and the albuminoids are converted into a form very difficult of digestion.
It is further stated by Olive that the chromosomes undergo longitudinal fission, and that for the same species the same number of chromosomes appear at each division.
The non-sexua 1 reproduction takes the form of fission, budding or sporogony, the details of which are described below.
But it was only after Darwin that the cell-theory of Schwann was extended to the embryology of the animal kingdom generally, and that the knowledge of the development of an animal became a knowledge of the way in which the millions of cells of which its body is composed take their origin by fission from a smaller number of cells, and these at last from the single egg-cell.
A division by fission followed by Endogenous spore formation, characteristic of the Schizosaccharomycetes.