Word Finder - segment

definition

A length of some object.

example

a segment of rope

definition

One of the parts into which any body naturally separates or is divided; a part divided or cut off; a section; a portion.

example

a segment of an orange;   a segment of a compound or divided leaf

definition

A portion.

definition

A portion.

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A part of a broadcast program, devoted to a topic.

example

The news showed a segment on global warming.

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An Ethernet bus.

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A region of memory or a fragment of an executable file designated to contain a particular part of a program.

definition

(travel) A portion of an itinerary: it may be a flight or train between two cities, or a car or hotel booked in a particular city.

definition

A bearing representing only one part of a rounded object.

definition

To divide into segments or sections.

example

Segment the essay by topic.

It is a little star-dust caught, a segment of the rainbow which I have clutched.

The whole mass lies in the seventh or eighth segment.

Apical cell, p. Wall marking limit between the plerome k, initial segment of root-cap. P and the pleriblem Pb.

In many of those ants whose third abdominal segment forms a second " node," the basal dorsal region of the fourth segment is traversed by a large number of very fine transverse striations; over these the sharp hinder edge of the third segment can be scraped to and fro, and the result is a stridulating organ which gives rise to a note of very high pitch.

Turning to the thorax we find that the first segment (prothorax) is distinct and free, with a wide dorsal sclerite.

As in the Oligochaeta the peristomial segment is often without setae; but this character is not by any means so constant as in the Oligochaeta.

In male beetles, however, the two pairs of genital processes (paramera) belonging to the ninth abdominal segment are always present, though sometimes reduced.

In these ants the difference between the large, heavy, winged males and females, and the small, long-legged, active workers, is so great, that various forms of the same species have been often referred to distinct genera; in Eciton, for example, the female has a single petiolate abdominal segment, the worker two.

It is, however, always possible to recognize a head, which consists at least of the peristomial segment with a forward projection of the same, the prostomium.

The prostomium overhangs the mouth, and is often of considerable size and, as a rule, quite distinct from the segment following, being A„ f s / 6/ ' A B I.

It is disputed whether these micronephridia are or are not connected together in each segment and from segment to segment.

Fielde show that an ant follows her own old track by a scent exercised by the tenth segment of the feeler, recognizes other inmates of her nest by a sense of smell resident in the eleventh segment, is guided to the eggs, maggots and pupae, which she has to tend, by sensation through the eighth and ninth segments, and appreciates the general smell of the nest itself by means of organs in the twelfth segment.

In the genera Pheretima, Megascolex, Dichogaster, &c., each segment contains a large number of nephridia, which, on account of the fact that they are necessarily smaller than the paired nephridia of e.g.

The nephridia are sometimes numerous in each segment.

The gonads are, moreover, limited and fixed in numbers, and are practically invariably attached to the intersegmental septa, usually to the front septum of a segment, more rarely to the posterior septum.

The sperm ducts are usually longer than the oviducts; but in Limicolae both series of tubes opening by the funnel into one segment and on to the exterior in the following segment.

The intestine has a pair of caeca or two or three pairs (but all lie in one segment) in the genus Pheretima and in one species of Rhinodrilus.

In Benhamia caecifera and at least one other earthworm there are numerous caeca, one pair to each segment.

The vascular system is simple with as a rule direct communication between dorsal and ventral vessels in each segment.

The annuli into which segments are externally divided are so deeply incised as to render it impossible to distinguish, as can be readily done in the Oligochaeta as a rule, the limits of an annulus from that of a true segment.

Each segment of the thorax carries a pair of legs.

There are no setae and apparently only two pairs of nephridia, of which the anterior pair open commonly by a common pore on the third segment after the head, whose segments have not been accurately enumerated.

Nephridia always paired, rarely (Pontobdella) forming a network communicating from segment to segment; lumen of nephridia always intracellular, funnels pervious or impervious.

This corre sponds to the usual pre sence (in the Rhyncho- bdellidae) of three annuli to each segment.

As remarked, the prevalent number of annuli to a segment is three in the Rhynchobdellidae.

In the Gnathobdellidae the prevailing number of annuli to a segment is five; but here again the number is often increased, and Trocheta has no less than eleven.

In Pontobdella and Branchellion the nephridia form a network extending from segment to segment, but there is only one pair of funnels in each segment.

The compound eyes of insects resemble so closely the similar organs in Crustaceans that there can hardly be reasonable doubt of their homology, and the primitively appendicular nature of the eyes in the latter class suggests that in the Hexapoda also they represent the appendages of an anterior (protocerebral) segment.

The maxillae of the hinder pair become more or less fused together to form a " lower lip " or labium, and the segment of these appendages is, in some insects, only imperfectly united with the head-capsule.

In some cases, however, it can be shown that the cerci really belong to an eleventh abdominal segment which usually becomes fused with the tenth.

The female genital opening usually lies in front of the eighth abdominal segment, the male duct opens on the ninth.

The fifth (distal) tarsal segment carries a median adhesive pad - the pulvillus - on either side of which is a claw.

Heymons (1895-1896) has proved by embryological study that in all cases they really belong to this eleventh segment, which in the course of development becomes fused with the tenth.

Smaller appendages (such as the stylets of male cockroaches) may be carried on the ninth segment.

An ear of another type is found in the swollen second segment of the feeler in many male gnats and midges, the cuticle between this segment and the third forming an annular drum which is connected with numerous nerveendings, while the fine bristles on the more distal segments vibrate in response to the note produced by the humming of the female.

The male opening is on the ninth abdominal segment, to which belong the processes that form the claspers or genital armature.

The antennal segment apparently entirely disappears, with the exception of a pair of appendages it bears; these become the antennae; it is possible that the original segment, or some part of it, may even become a portion of the actual antennae.

One of these is the ocular segment, in front of the antennal, and behind the primitive preoral segment.

Great difference of opinion exists as to the hypopharynx, which has even been thought to represent a distinct segment, or the pair of appendages of a distinct segment.

The thoracic segments, as seen in an early stage of the ventral plate, display in a well-marked manner the essential elements of the insect segment.

The cerci, when present, appear in the mature insect to be attached to the tenth segment, but according to Heymons they are really appendages of the eleventh segment, their connexion with the tenth being secondary and the result of considerable changes that take place in the terminal segments.

The stylets, when present, are placed on the ninth segment, and in some Thysanura exist also on the eighth segment; their development takes place later in life than that of the cerci.

In some embryos there is but a single pair of these rudiments (or vestiges) situate on the first abdominal segment, and in some cases they become invaginations of a glandular nature.

The continuous layer of cells from which the nervous system is developed undergoes a segmentation analogous with that we have described as occurring in the ventral plate; there is thus formed a pair of contiguous ganglia for each segment of the body, but there is no ganglion for the telson.

But the protocerebrum contains the ganglia of the ocular segment in addition to those of the procephalic lobes.

The ejaculatory duct which opens on the ninth abdominal sternum in the adult male arises in the tenth abdominal embryonic segment and subsequently moves forward.

First abdominal segment united to metathorax.

They differ from other Endopterygota in the multiplication of their Malpighian tubes, and from all other Hexapoda in the union of the first abdominal segment with the thorax.

Further examination also revealed the fact 3 that in certain groups the number of " primaries," or quill-feathers growing from the manus or distal segment of the wing, formed another characteristic easy of observation.

These glands are represented externally by a special plate, the cribellum, which lies in front of the ordinary spinning mamillae, and by a comb of short bristles, the calamistrum, placed in the penultimate segment of the left of the last pair.