isoclinal 
Isoclinal Lines for 1890. 
Isoclinal lines, in magnetism, lines drawn upon a map 
through points at all of which the dip of the needle is the 
same. 
II. n. Same as isocline. 
The directions of the isogonals, isoclinals, and lines of 
equal horizontal force have been found. 
Nature, XXXIX. 565. 
Also isoclinic. 
isocline (I'so-klin), . [< Gr. laof, equal, + 
i&iveiv, incline: see dine.] In geol., a fold in 
which the strata are so appressed that the limbs 
or flanks (the parts on each side of the axis of 
the fold) are isoclinal, or dip in the same direc- 
tion. See monocline. Also called overturn, or 
overturned anticlinal. 
isoclinic (I-so-klin'ik), a. and n. [< isocline + 
-ic.] Same as isoclinal. 
The isoclinic lines of the globe run round the earth like 
the parallels of latitude, but are irregular in form. 
S. P. Thompson, Elect, and Mag., p. 117. 
The whole region . . . would have to be surveyed in 
order to permit the tracing out of isoclinics. 
Science, IX. 217. 
isoclinostat (I-so-kli'no-stat), . [< Gr. laof, 
equal, + Mveiv, incline, + arar&f, verbal adj. of 
lar&vfu, stand : see static."] A link-work for di- 
viding any angle into equal parts. Also iso- 
Minostat. 
iSOCOlic (l-so-ko'lik), a. [< isocolon + -ic.~\ 1. 
In rhet., containing successive clauses of equal 
length: as, an isocolic period. 2. Inane. pros., 
consisting of series or members all of the same 
magnitude : as, an isocolic system. See isocolon. 
isocolon (i-so-ko'lon), n.; pi. isocola (-la). [< 
Gr. ia6nu'Aov, neut. of laonu/.of, of equal mem- 
bers or clauses, < loof, equal, + nutov, a member, 
limb, clause: see colon 1 .] 1. In rhet.: () A 
figure which consists in the use of two or more 
clauses (cola) in immediate succession having 
the same length or number of syllables. If the 
equality is only approximate, the figure is prop- 
erly called parison or parisosis. (b) A period 
containing successive clauses of equal length. 
2. In anc.pros., a period or system consisting 
of cola or series of the same length throughout. 
isocrymal (I'so-kri-mal), n. [< isocryme + -al.~\ 
A line, imaginary or drawn upon a map or chart 
of any region, connecting points at which the 
temperature is the same during some specified 
coldest portion of the year. The word was intro- 
duced by J. D. Dana, and used by him with reference to 
the mean temperature of the ocean surface "for the cold- 
est thirty consecutive days of the year." 
It is unnecessary to remark particularly upon the fit- 
ness of the other isocrymoJs for the purpose of illustrating 
the geographical distribution of marine species. 
Dana, Amer. Jour. Sci. (2), xvl. 157. 
isocryme (I'so-krim), n. [< Gr. laof, equal, + 
Kpvfiof, cold, chill (cf. /cpi'iof, cold, frost): see 
crystal.'} Same as isocrymal. 
The isocryme of 68 is the boundary line of the coral- 
reef seas. Dana, Amer. Jour. Sci. (-2), xvi. 156. 
isocyclous (I-so-si'klus), a. [< NL. isoeyclus, 
< Gr. ioof, equal, + KvK^of, circle : see cycle 1 .'] 
Composed of successive equal or similar rings. 
isoeyclus (i-so-si'klus), . [NL., < Gr. "toot, 
equal, + KM/IOC, circle.] An animal the body 
of which consists of a series of equal or similar 
rings. Sir B. Owen. 
isodactylous (5-so-dak'ti-lus). a. [< NL. iso- 
dactylus, < Gr. laof, equal, + daKTv/.oc, digit.] In 
zool., having the toes or digits of equal length or 
otherwise alike : its opposite is anisodactylous. 
Isodia (i-so'di-a), B. pi. [< MGr. daoSta, neut. 
pi. of Gr. elaodiof, pertaining to entrance, < tiao- 
(5of, entrance, in MGr. the feast of the entrance 
of the Virgin Mary into the temple, < cif, into, 
+ t>66f, way.] In the Gr. Ch., the feast of the 
Presentation of the Theotocos or Blessed Vir- 
fin Mary in the temple, observed November 
1st. See presentation. Also written Eisodia. 
isodiabatic (I-so-dl-a-bat'ik), a. [< Gr. laof, 
equal, + dz/far<if , able to pass through, < Sia- 
/3arof, verbal adj. of Sutdaivetv, pass through : 
see diabaterial.] Pertaining to the transmis- 
3196 
sion to or from a body of equal quantities of 
heat. Thus, isodiabatic parts of isothermal curves are 
parts which represent changes of pressure and density of 
the same body during the transmission of equal quanti- 
ties of heat, the temperature remaining constant, 
isodiainetric (i-so-di-a-met'rik), a. [< Gr. laof, 
equal, + Aiduerpof, diameter: see diameter.] 
Having equal diameters, or being of equal di- 
ameter. Specifically (a) In crystal., pertaining to crys- 
tals having equal lateral axes, as crystals of the tetragonal 
or hexagonal systems, which are optically uniaxial. (b) 
In tot., having the diameter similar throughout, as organs 
or cells. 
The tissue when fully formed consists of iaodiametric 
roundish or polyhedral cells. De Bary, Fungi (trans.), p. 3. 
isodiametrical (I-so-di-a-met'ri-kal), a. [< iso- 
diametric + -al.] Same as isodtametric. 
There are cells which are especially concerned in assim- 
ilation, and which may be either iso-diametrical or elon- 
gated in a direction either parallel to or at right angles 
with the axis. Jour. Roy. Micros. Sue., 2d ser., VI. i. 10. 
isodicon (i-sod'i-kon), n. ; pi. isodica (-ka). [< 
MGr. eiao6iK6v, neut. of claodiKof, pertaining to 
the entrance, < Gr. eiaodof, entrance : see Iso- 
dia.] In the Gr. Ch., a troparion or brief an- 
them succeeding the third antiphon and ac- 
companying the Little Entrance. See entrance. 
Also written cisodicon. 
isodimorphism (I"so-di-m6r'fizm), . [< Gr. 
laof, equal, + E. dimorphism.] In crystal., 
isomorphism between the members of two di- 
morphous groups. 
isodimorpnous (I'so-di-mdr'fus), a. [< Gr. laof, 
equal, + E. dimorphous.] In crystal., having 
the quality of isodimorphism. 
isodomon, isodomum (l-sod'o-mon, -mum), n. 
[< Gr. laoSofiov, iieut. of iaodo/tof, built alike, < 
laof, equal, + 6l- 
fitiv. build, > 66/iof, 
do/tq, a building : 
see dome 1 .] One 
of the varieties of 
masonry uscJd in 
the best period of 
Greek architec- 
ture, in which the 
blocks forming the 
courses were of 
equal thickness and equal length, and so dis- 
posed that the vertical jojnts of an upper course 
came over the middle of the blocks in the course 
below it. See pscudisodomon. 
isodomous (i-sod'o-mus), a. [< isodomon + 
-ous.] Of the nature of isodomon. 
A great part of the city-wall, built in flue Hellenic isodo- 
mous masonry, and a large square central fortress with a 
circular projecting tower, are the only remains now trace- 
able. Eneyc. Brit., XVIII. 735. 
isodont (I'so-dont), a. [< Gr. laof, equal, + bdoif 
(bdovr-) = E\ tooth.] Having the teeth all alike, 
as a cetacean; having the characters of the 
Isodontia. 
Isodontia (i-so-don'shi-a), n. pi. [NL., < Gr. 
laof, equal, + bdov; (bfiovr-) = E. tooth.] In 
Blyth's edition of Cuvier, an order of placeutal 
mammals, consisting of the Cetacea of Cuvier 
minus the herbivorous cetaceans (sireuians) of 
that author; one of two orders constituting 
Blyth's zoophagous type of mammals. [Not 
in use.] 
isodynamic (i"so-di-nam'ik), a. and n. [< Gr. 
laoSvvafiof, having equal power or force : see iso- 
dynamous.] I. a. Having equal power or force; 
relating to equality of force Isodynamic lines, 
in magnetism, lines connecting those places where the 
b 
with blocks secured by 
dowels. 
Isodynamic Lines for 1890. 
intensity of the force of terrestrial magnetism is equal. 
They have a certain general resemblance in form and 
position to the isoclinal lines. 
II. n. An isodynamic line, 
isodynamous (i-so-di'na-mus), a. [< Gr. laodv- 
fo/iof, having equal power or force, < laof, equal, 
+ Siva/ttf, power, force: see dynam, dynamic.] 
Having equal force ; of equal size ; in hot. , same 
as isobrious. 
Isoeteae(I-so-et'e-e), n.pl. [NL.,< Isoetes + -eai.] 
An order of vascular cryptogamous plants, re- 
isogonic 
lated to the Selaginellacea', containing the sin- 
gle genus Isoetes. 
Isoetes (i-so'e-tez), . [NL., < L. isoetes, small 
houseleek or aye-green, < Gr. woirrif, equal 
in years (ueut. TO laocrff, an annual plant), < 
laof, equal, + srof, a year.] A genus of vas- 
cular cryptogamous plants, belonging to the 
natural order 
Isoetea;. They are 
small grass-like or 
rush-like aquatic 
or semi-aquatic 
plants, in which 
the plant-body con- 
sists of an exceed- 
ingly restricted 
stem, which gives 
off a dense mass of 
roots from below 
and sends up acorn- 
pact tuft of leaves 
above. The spo- 
rangia are sessile 
in the axils of the 
leaves, and some 
contain macro- 
spores (mega- 
spores) and some 
microspores. The 
genus comprises 
about 50 species, 
and has a very wide 
geographical dis- 
tribution, occur- 
ring in Europe, 
Asia, Australasia, 
Africa, and North 
and South Ameri- Quillwort ( 
ca. The species, <*. sporangium cut longitudinally, showing 
which rp irpm.nl the luacrospores or megaspores ; *, sporan- 
iTktwn 3 STSSL ~' SS&S8KKSI . Scro. 
worts, are of no 
especial value. /. lacustris is known in England as Mer- 
liris-grass. Some half-dozen species have been found in a 
fossil state, chiefly in the Tertiary of Europe, but one oc- 
curs in the Eocene of Colorado, one in the Upper Jurassic 
of Bavaria, and another in the Oolite of Yorkshire, Eng- 
land. These lower forms are usually distinguished by the 
name Isoetites. 
isogamous (i-sog'a-mus), a. [< Gr. laof, equal, 
+ ydfiof, marriage.] Characterized by isog- 
amy. The isogamous algse are the Zygnemea; 
Desmidiea!, etc. 
ISOgamy (i-sog'a-mi), n. [< Gr. laof, equal, + 
jd/iof, marriage.^] In bot., the conjugation of 
two gametes of similar form, as in certain alge. 
Compare oogamy. 
isogenous (i-soj'e-nus), a. [< Gr. laofevf/f, equal 
in Kind, < laof, equal, + yevof, kind : see -genoits.] 
Of the same or a similar origin; homologous, 
in a broad sense, as formed from the same or 
corresponding tissues of the embryo. Thus, parts 
of the nervous system of worms, mollusks, and vertebrates 
are isogenoiw, being derived from the epiblast. 
isogeny (i-soj'e-ni), n. [As isogen-ous + -y.] 
In biol., similarity or identity of origin; origi- 
nation in or derivation from the same or corre- 
sponding tissues ; evolutionary homology, in a 
broad sense. 
It is well to use words which will express our meaning 
exactly, and hence a general homology may be indicated 
by the word isogeny, indicating a general similarity of ori- 
gin. Stand. Ufat. Hist., I., Int., p. xvii. 
isogeotherm (I-so-je'o-therm), n. [< Gr. laof, 
equal, + yy, the earth, + Qep/ai, heat.] In phys. 
geog., an imaginary line or surface under the 
earth's surface passing through points having 
the same temperature. 
isogeothermal (i-so-je-o-ther'mal), a. [< iso- 
geotherm + -al.] Inpliys. geog., pertaining to 
or having the nature of an isogeotherm. 
isogeothermic (i-so-je-o-ther'mik), a. [< iso- 
geotherm + -ic.] Same as isogeothermal. 
ISOgnathous (I-sog'na-thus), a. [< Gr. laof, 
equal, + yvdtiof, jaw.] In odontog., having the 
molar teeth alike in both jaws : opposed to an- 
isognathoi's. 
isogon (i'so-gon), n. [= Sp. It. isogono; < Gr. 
iaoywviof, having equal angles, < iaof, equal, + 
yuvia, angle.] In math., a figure whose angles 
are equal. 
isogonal (I-sog'o-nal), a. and . [< isogon + 
-al.] I. a. Having equal angles. 
II. n. An isogonic line. 
isogonic 1 (i-so-gon'ik), a. [< isogon + -ic.] 
Having equal angles. isogonic lines, in magne- 
ti*m, lines on the earth's surface at every point of which 
the deviation of the magnetic needle from the true north 
is the same for a given period. See cut on following page. 
On the globe the isogonic lines run for the most part 
from the north magnetic pole to the south magnetic polar 
region. 5. P. Thompson, Elect, and Mag., p. 117. 
isogonic 2 (i-so-gon'ik), a. [< Gr. laof, equal, 
+ yovof, offspring.] In biol., exhibiting isog- 
onism; producing identical generative indi- 
viduals from different stocks, as hydroids of 
different families may do. 
