Rhizopod Protozoa (?) with filamentary tracks and travelling spindles.
A group Labyrinthnleae was established, in 1867, by Cienkowski for the reception of Labyrinthula, an organism discovered by him growing upon piles in the harbour of Odessa. A somewhat similar organism, Chlamydo-myxa, has been found by Archer in Westmeath and Connemara, infesting the leaves, etc. of Sphagnum and other freshwater plants; it has also been recently observed by Ray Lankester at Pontresina in the Engadine.
There are two species of Labyrinthula, L. vitellina and L. macrocystis. The former lives at the level of the watermark, and in the resting condition appears as reddish-yellow masses about the size of a pin's head. If such a mass is placed in water for twenty-four hours, it passes into a motile condition; and when examined under the microscope, is seen to consist of a central mass whence there extends towards the periphery of the drop of water an open network of filamentary tracks. Moving along these tracks at a rate of about 1/40-1/80 mm.per minute are yellow spindles which collect here and there into outlying groups. The central mass consists of a finely granular matrix imbedding numbers of yellow or brick-red globular cells .oI2 mm. in diameter, with a nucleolated nucleus and an envelope which stains brown with Iodine. When fresh they are stained blue by the same reagent. These cells assume a spindle-shape and wander from the central mass, which undergoes meanwhile no visible change along the filamentary tracks, as above stated, until in a few hours' time they have all, or at any rate the majority of them, quitted it. They multiply by binary fission.
The filamentary tracks are glassy in appearance, homogeneous or fibrillate, rigid and unchanging; whether tubular or composed of fibrils lying at some distance apart, Cienkowski could not determine. Whatever their nature, they appear to consist of the same substance as the matrix of the central mass, not protoplasmic, but rather a secretion. Cienkowski states that after the wandering of the spindles is completed, the tracks become invisible in some places, in others, where there are isolated spindles or masses of spindles, gelatinous; that individual spindles or naked spindle-masses are capable of forming tracks, and that when the organism grows under water the amount of matrix is greatly increased. The motile condition of the organism was found naturally existing among the colonies of Campanularians and on the eggs of Tergipes.
L. macrocystis lives at some distance above the watermark. It differs from the foregoing species in the following particulars. Its resting-phase has the form of yellowish or white vermiform masses. Its cells are larger, .018 - .025 mm. in size, their nuclei more sharply defined, their contents more granular, colourless or feebly yellow, and not stained blue by Iodine, It passes readily into a quiescent encysted stage. The cells then enlarge, turn more granular, and display a more pronounced tint; finally they become ovate and .035 mm. long. Each of them secretes a smooth thick membrane, whilst the matrix becomes firm and superficially granular. If such an encysted mass is placed in water each cell in about six weeks' time divides into four parts, which are set free as motionless globular cells by the gradual absorption of the cyst-membrane. The cells appear to change into spindles which, whether single or in masses, produce filamentary tracks along which they move 1
Chlamydomyxa like Labyrinthula has a resting and a motile phase. It has, however, in the former condition the power of growing. The smallest encysted examples have the form of minute spherical bodies of a green colour, with or without a red granule, inclosed by a delicate cellulose membrane. Such bodies occur free when they grow for some time without losing their spherical shape, or else lodged within the cells of, e. g. a Sphagnum leaf. In this case they elongate, but at last force their way outwards to the surface of the leaf where they protrude. The protrusion increases in size by degrees, and finally the protoplasm may be withdrawn entirely from the portion of the cyst which remains within the leaf. During growth fresh laminae of cellulose are continually laid down within the membrane first formed. Encysted examples with the structures described are most variable in shape. The contents of a cyst may divide into equal or unequal parts, everyone of which surrounds itself with a cellulose membrane. The number of red granules increases, and it not infrequently happens that some of them become inclosed within layers of cellulose producing internal wart-like growths. In some instances the cysts acquire a ruddy hue.
The motile condition has been seen only by Archer. The envelopes of the cyst burst at some one point, its contents push forth a stem which branches and spreads, the branches in turn giving origin to delicate, widely-extended, and ramified filamentary tracks. The last-named, though flexible, do not change their shape or do so but slowly. The contents of the ruptured cyst are, according to Archer, a hyaline protoplasm with an amorphous greenish substance, yellow-green granules, red granules, and great number of pale-blue globules. There is no nucleus but the stem and its branches possess a number of contractile vacuoles. The pale-blue and non-nucleated globules transform themselves into spindles which wander along the tracks; they change their shape when they reach a point where a track bifurcates. Their motion may cease or become retrograde, and they may, as in Labyrinthula, collect in outlying masses. The whole structure, tracks, spindles, branches, and stem may be withdrawn into the cyst; and it may happen that outlying masses are cut off and left behind.
From Archer's statement it appears certain that Chlamydomyxa has the power of digesting such organisms as Cosmarium which may be carried with the protoplasm into the cyst.
1Brandt has suggested that the yellow cells of the Radiolarian Acanthometra tetracopa are identical with the spindles of L. vitellina; Mitth. Zool. Stat. Naples, iv. 1883, p. 239.
Though there are undeniable resemblances between Labyrinthula and Chlamydomyxa, yet there are certain differences which make it possible that the two ought not to be classed together. In one the spindles are nucleated cells, the matrix and tracks apparently a secretion. In the other the spindles are non-nucleated, the tracks, the branches, and stem from which they spring protoplasmic; there are contractile vacuoles and other organisms may serve as food1.
Labyrinthula, Cienkowski, A. M. A. iii. 1867; cf. Q. J. M. xv. pp. 12L-4. Chlamydomyxa, Archer, Q.J. M. xv. 1875; Geddes, ibid. xxii. 1882; at Pontresina, Ray Lankester, Nature, xxxiv. 1886, p. 408.