19, F) which tie the axial pharynx to the adjacent wall of the apical part of the introvert.
It is terminated by a well-developed structure (fg) corresponding with the apical sense-organ of ordinary Trochospheres, and an excretory organ (nph) of the type familiar in these larvae occurs on the ventral side of the stomach.
Tail long, its apical half-clothed on the dorsal surface with long hairs.
In the Fucaceae, on the other hand, there is a single prismatic apical cell situated at the bottom of a groove at the growing apex of the thallus, which cuts off cells from its sides to add to the peripheral, and from its base to add to the central permanent cells.
The whole of the tissue of the plant is formed by the division of this apical cell.
The group, the exceptions being met with almost entirely among the higher Brown Seaweeds, in which is found parenchyma produced by the segmentation of an apical cell of the whole shoot, or by cell division in some other type of meristem.
It always consists of true parenchyma, and is entirely formed by the cutting off of segments from an apical cell.
On germination of the seed the radicle first grows out, increasing in size as a whole, and soon adding to its tissues by cell division at its apical growing-point.
Further growth in length of the stem is thenceforward confined to the apical growing point situated between the cotyledons.
The structure of the growing-points or apical meristems varies much in different cases.
In some Pteridophyte stems the apical eel is wedge-shaped, in others prismatic; in the latter case segment~
In other cases, again, a group of two or four prismatIl cells takes the place of the apical cell.
The separation of layers in the apical meristem of the root is usually very much more obvious than in that of the stem.
The branches of the stem arise by multiplication of the cells 01 the epidermis and cortex at a given spot, giving rise to a protuber ance, at the end of which an apical meristem is established.
The growth of the leaf is at first apical, but this is not very prolonged, and the subsequent enlargement is due to an intercalary growing region near the base.
The lower Cryptogams were contrasted as Amphigenae ("growing all over"), a misnomer, as apical growth is common among them.
ANT-LION, the name given to neuropterous insects of the family Myrmeleonidae, with relatively short and apically clubbed antennae and four large densely reticulated wings in which the apical veins enclose regular oblong spaces.
Ap. Apical organ.
- The 3rd, 4th, 5th and 6th pairs of appendages short, stout, tapering, the segments about as wide as long, except the apical, which is distally slender, pointed, slightly curved, and without distinct movable claws.
- The 3rd, 4th, 5th and 6th pairs of appendages slender, not evenly tapering, the segments longer than wide; the apical segment short, distally truncate, and provided with a pair of movable claws.
Coxal (maxillary) process, the apical segment tipped with a single movable or immovable claw; appendages of 3rd pair different from the remainder, tactile in function, with at least the apical segment many-jointed and clawless.
Appendages of 2nd pair with their basal segments united in the middle line and incapable of lateral movement; appendages of 3rd pair with only the apical segment many-jointed.
Intromittent organ of male in the apical segment of the 2nd prosomatic appendage.
The apical senseorgan is used for temporary attachment to the maternal vestibule in which development takes place, but permanent fixation is effected by the oral surface.
Fg, Apical sense-organ.
A circular piece of this paper is folded twice upon itself so as to form a quadrant, one of the folds is pulled out, and the cone thus obtained is supported in a glass or porcelain funnel having an apical angle of 60°.
- In this division the body is partly covered by a broad shield, united in front with the head; the eyes are sessile, the first antennae are small, the second rudimentary or wanting; of the numerous feet, sometimes sixty-three pairs, exceeding the number of segments to which they are attached, the first pair are more or less unlike the rest, and in the female the eleventh have the epipod and exopod (flabellum and sub-apical lobe of Lankester) modified to form an ovisac. Development begins with a nauplius stage.
The apical end of the rotifer usually narrows suddenly beyond the curve of the gut and the cloacal aperture to form the foot of pseudopodium which ends in an organ of attachment, a pair of movable toes, each with the opening of a cement-gland (gl) at its tip. Thus for orientation we place the rotifer like the cuttle-fish, head downwards: the ciliated disk is basal or oral, proximal to the rest of the animal, the foot is apical, and the brain and cloacal aperture are anterodorsal.
Of Turbellaria and Ne- a, anus; ap, apical organ, correspond mertina.
We may note that it was long since shown that the apical organ (at first assumed to be the brain) of these larvae was innervated from an anterior thickening of the circular nerve ring, corresponding with the brain of Rotifers; the nerve cells immediately below the pit are the ordinary bipolar From H.
Asplanchnopus myrmeleo, showing horseshoe-shaped germarium (left), blind saccate stomach (right), apical bladder, foot, &c.; g, Asplanchna ebbesbornii - the coiled tube at left is a kidney; h, i, incudate jaws of Asplanchna brightwellii and girodii chiefly formed of rami, with the rudimentary mallei parallel and external to them; j, Ascomorpha hyalina.
In Dictyota, Sphacelariaceae and Fucaceae there is a definite apical cell.
While, however, in Dictyota the product of the subsequent division in the segment enlarges with each subdivision, the divisions in the cylindrical segment of Sphacelariaceae are such that the whole product after subdivision, however many cells it may consist of, does not exceed in bulk the segment as cut off from the apical cell.
In Dictyotaceae the apical cell occasionally divides longitudinally, and thus the dichotomous branching is provided for.
In some Sphacelariaceae branches may appear at their inception as lateral protuberances of the apical cell itself.
In Fucaceae an apical cell is situate at the surface of the thallus in a slit-like depression at the apex.
Halopteris, apical region.
Dictyota sp., apical cells immediately after dichotomy.
Chara sp., apical region.
Attached to the bottom of pools series of the Confervales, the thallus consists of filaments branched by means of rhizoids, the thallus of Characeae grows upwards by or unbranched, attached at one extremity, and growing almost means of an apical cell, giving off whorled appendages at regular wholly at the free end.
In Coleochaete the oogonial wall is drawn out into a considerable tube, which is provided with an apical pore, and this tube has a somewhat similar appearance to the imperforate trichogyne of Florideae to be hereafter described.
The signification of the coalescence of the polar nuclei is not explained by these new facts, but it is noteworthy that the second male-cell is said to unite sometimes with the apical polar nucleus, the sister of the egg, before the union of this with the basal polar one.