;f>2 
H E L 
known. One of tliefe, Bur/aria duplella , is represented 
at fig- 15- ^ is of an elliptical figure, with the edges 
folded over, leaving a narrow lAngitudinal cavity ; 
browni.fh : found on duckweed’. 
Gonium. This genus contains five fpecies, which 
are either of a quadrangular or orbicular figure, filled 
with Spherical molecules, fet in a pellucid membrane 
like.diamlpnds in'a ring. The fpecies are defcribed under 
Gonium, vol.viii. p.67j; and a figure of one of them 
is given in the Engraving adapted to that article. 
Colpoda. This is a pellucid flat worm,, 'of which 
there are Seven fpecies. One of them, Colpoda cucullus, is 
exhibited in the annexed Engraving at fig. 16. It is of 
an ovate figure, with an irregular margin, the top bent 
into a kind of beak ; the membrane pale blue, filled 
with about twenty-four bright molecules : found in ve¬ 
getable infufipns. 
Paramecium. This is alfo a genus of flattened 
worms, containing feven fpecies; one of which, Para¬ 
mecium chrysalis, is corredlly represented in the Engraving 
at fig. 17. It is longitudinally plaited on the fore-part, 
and obtufe behind ; the margins filled with opaque glo¬ 
bules, w hich are the ovaries or embryos of this tribe of 
invifibles: found in putrid fait water; pale red. 
Cycudium. The worms of this genus are either 
ovate of orbicular, flat, pellucid, and very Simple. There 
are feven Species; Some of which .are fo' exceflively mi¬ 
nute as to elude the powers of the ftrongeft: magnifier in 
defining their parts. The Cyclidium pcdiculus is ascertain¬ 
ed to be a white gelatinous worm, found on the Hydra 
fufca. This polype, in its quiefcent date, is delineated 
in the Engraving at fig. 18, on purpofe to fliow the con¬ 
geries of tliefe minute animalcules which Seem deflined 
to maintain their exiftence upon it. See alfo the article 
Cyc lidium, vol. v. p. £08, ayd the correspondent En¬ 
graving at fig. 24, for other Species of this worm. 
Vibrio. This genus confifis of worms equally if 
not more minute than the preceding. They are chiefly 
linear or filiform, and poflefs a kind of Serpentine form 
and motion. Twenty fpecies have been ascertained, 
found chiefly in vegetable infufions, or iri foul ftagnant 
water, or putrid vegetable matter, Such as pafte, vine¬ 
gar, &c. One of tliefe is exhibited in the annexed En¬ 
graving, at fig. 19, Vibrio gliitinis, yellowifli white, found 
in pafte kept for Some time; and in any Sediment of 
wheat or other grain. Another -Species is given, more 
considerably magnified, at fig. 20, Vibrio aceti, found in 
vinegar, and other mild acids. It is of a greenilh yel- 
- low, with a white line from the head to the abdomen ; 
and its tail is pointed, with a retradlile protuberance at 
the bafe. It is very adlive and fertile, being both vi¬ 
viparous and oviparous. 1 • \ 
Leucophra. This is a genus of invisible worms of . 
various figures, but all of them ciliate or hairy. There 
are eight fpecies; one of which, Leucophra vejiculifera, is 
delineated in the Engraving at fig. 21; it is ovate, pale 
blue, full of minute veficles, and finely ciliate on the 
edges. Another Species is Shown at fig. 22, Leucophra 
hctcroclita, rounded and obtufe, and furnilhed with a 
double exfertile organ, with ftellate rays, ciliate on the 
edges; the inteftines’are vifible through the membrane, 
which is pale red. 
B ac 1 l lari a. Of this genus there is only one fpecies 
at prefent known, denominated Bacillaria paradoxa. Its 
body confifis of cylindrical ftraw-like filaments, laid 
parallel to each other ; but which the animal has the 
power of expanding and changing into various pofitions, 
yet always lo as to preferve their parallelism, whether 
tiie body be lengthened, widened, or formed into a 
Square. This Singular worm is delineated in the En¬ 
graving at fig. 23^ in its linear or cylindrical* ft’a^te ; and 
at fig. 24, in an expanded form, which it perpetually 
varies while in v.l tion. 11 is generally of a greeniili-yel- 
low colour, and found adhering to the Viva latijj'cma. 
Enchelis. This genus contains fifteen ipecies of 
H E L 
invifible naked worms, moftly of a cylindrical figifre, 
and very fimple. One of them, Enchelis truncus , is exhi¬ 
bited in the Engraving at fig. 25; body pale grey, thfe 
fore-part globular, hind-part obtufe, With three denticles 
or toothed fpines protruded upwards; beneath which 
are feen a number of globules, fuppofed to be the ova¬ 
ries: found in ftagnant waters. Three other fpecies are. 
figured in the Plate of the Egle marmelos, adapted to the 
article Enchelis, vol.vi. p.288, and 518. 
VolvOx. The worms of this genus are either glo¬ 
bular, hemifpherical, or lunular; very fimple, and pel¬ 
lucid. There are nine fpecies, one of which, Volvox 
lunula, is delineated in the Engraving at fig. 2 6. It,con- 
Sifts of a pellucid membrane, pale yellow, filled with 
crefcent-fliaped molecules, and has a double motion, 
that of the whole mafs turning flowly round, and of the 
molecules one among another: found in marlh water» 
Another fpecies is exhibited at fig. 27, Volvoxfphcsrula t 
appearing as a pellucid greenifh yellow membrane or 
halo, filled with circular molecules ; moves flowly about 
a quarter of the circle from right to left, and then back 
again from left to rightfound in ftagnant waters. 
Monas. This genus is fuppofed to contain the mi- 
nuteft-of all the worms hitherto inveftigated by natiw 
ralifts. They appear but as a moving point in the wa¬ 
ter ; and it was a long time before their animation could 
be fatisfadlorily aftertained. There are five fpecies, 
one of which, Monas atomus, is reprefented in the En¬ 
graving at fig. 28. It has the appearance of a light- 
green halo, filled with numerous pellucid atoms, with 
a black dot in moveable pofitions; and is found in fea- 
water after it has been kept a confiderable time. Monas 
lermo, is the moll minute of the genus; being fo ex¬ 
tremely fmall and tranfparent, as often to elude the mo.fi 
highly magnifying powers in endeavouring to render it 
vifible, fo much does it blend or aflimilate with the wa¬ 
ter in which it fwirns. 
The numerous' fpecies contained in each of the pre¬ 
ceding genera, are defcribed under the article Animal¬ 
cule,- vol. i. p. 717-729; where the reader will alfo 
find explained the feveral hypothecs of Leeuwenhoek, 
Hartfoeker, Buff'on, and others, concerning the dodtrine 
of organic particles, and fpcrmatk animalcules. Since the 
arrangement was drawn up by O. F. Muller, in the 
above-mentioned article, Dr. Gmelin of Gottingen has 
new-modelled the Linnaean Order of Infuforia, as now- 
given ; in which he has feparated many individuals 
from Muller’s claftificatiqii, that are mere varieties of' 
the fame animal; and others which belonged'to diffe¬ 
rent or diftindl genera. Thefe are each of them further 
explained, and illuftrated with Engravings, under their 
refpedtive titles in this Encyclopaedia. 
HELMINXIIOTHE'C'A and HLLMIN'TIA,/. in 
botany-. SeePiCRis. 
HEL'MONT, a town of Brabant, filtrated on the Aa, 
with an old caftle, which belonged to the houfe of Cor- 
tembacli: eight leagues fouth-eaft from Bois-le-Duc. 
HEL'MONT (John Baptift Van), a diftingtiilhed phy- 
fieian, born of a noble family at Bruflels, in 1577. He 
received his education at Louvain, and read public lec¬ 
tures upon furgery in his feventeenth year; and was 
created dodlor of phyfic in the fame univerfity in 1599. 
His earlieft publication was a work on the Spa waters-,, 
printed at Liege in 1624. In this he is the firfi: author 
who takes notice of their volatile fpirit, to which he 
gave the name of gas, now become a generical term in 
chemiftry. He continued to publiih a variety of works, by 
which he acquired great reputation. The eledloral arch- 
bifliop of Cologn, who was fond of chemical enquiries, 
highly efteemed him; and he received from theempe-^ 
ror Rodolph and two other emperors, invitations to the 
court of Vienna, which he declined accepting, tie died 
in 1644, in his fixty-eighth year. He was a man of an 
acute genius; and in chemiftry he made confiderable 
additions to the flock of known fadts, and opened the 
way 
