The Acanthocephala are dioecious. There is a ``stay'' called
the ``ligament'' which runs from the hinder end of the
proboscis sheath to the posterior end of the body. In this the two testes
lie (fig. 3). Each opens in a vas deferens which bears three
diverticula or vesiculae seminales, and three pairs of cement
glands also are found which pour their secretions through a duct into
the vasa deferentia. The latter unite and end in a penis which opens
posteriorly.
Fig. 3.---An optical section through a male Neorhynchus
clavaeceps, Zed. (from Hamann).
a, Proboscis.
b, Proboscis sheath.
c, Retractor of the proboscis.
d, Cerebral ganglion.
f, f, Petractors of the proboscis sheath.
g, g, Lemnisci, each with two giant nuclei.
h, Space in sub-cuticular layer of the skin.
l, Ligament.
m, m, Testes.
o, Glands on vas deferens.
p, Giant nucleus in skin.
q, Opening of vas deferens.
The ovaries arise like the testes as rounded bodies in the
ligament. From these masses of ova dehisce into the body
cavity and float in its fluid. Here the eggs are fertilized
and here they segment so that the young embryos are formed
within their mother's body. The embryos escape into the
uterus through the ``bell,'' a funnel like opening continuous
with the uterus. Just at the junction of the ``bell''
and the uterus there is a second small opening situated
dorsally. The ``bell'' swallows the matured embryos and
passes them on into the uterus, and thus out of the body via
the oviduct, which opens at one end into the uterus and at
the other on to the exterior at the posterior end of the
body. But should the ``bell'' swallow any of the ova, or
even one of the younger embryos, these are passed back
into the body cavity through the second and dorsal opening.
The embryo thus passes from the body of the female into
the alimentary canal of the host and leaves this with the
faeces. It is then, if lucky, eaten by some crustacean, or
insect, more rarely by a fish. In the stomach it casts
its membranes and becomes mobile, bores through the stomach
walls and encysts usually in the cavity of its first and
invertebrate host. By this time the embryo has all the
organs of the adult perfected save only the reproductive;
these develop only when the first host is swallowed
by the second or final host, in which case the parasite
attaches itself to the wall of the alimentary canal and
A curious feature shared by both larva and adult is the large
size of many of the cells, e.g. the nerve cells and the bell.
O. Hamann has divided the group into three
families, to which a fourth must be added.
(i.) Fam. Echinorhynchidae.This is by far the largest
family and contains the commonest species; the larva of
Echinorhynchus proteus lives in Gammarus pulex and in
small fish, the adult is common in many fresh-water fish: E.
polymorphus, larval host the crayfish, adult host the duck:
E. angustotus occurs as a larva in Asellus aquaticus,
as an adult in the perch, pike and barbel: E. moniliformis
has for its larval host the larvae of the beetle Blaps
mucronata, for its final host certain mice, if introduced
into man it lives well: E. acus is common in whiting: E.
porrigeus in the fin-whale, and E. strumosus in the seal.
A species named E. hominis has been described from a boy.
(ii.) Fam. Gigantorhynchidae. A small family of large forms
with a ringed and flattened body. Gigantorhynchus gigas
lives normally in the pig, but is not uncommon in man in
South Russia, its larval host is the grub of Melolontha
vulgaris, Cetonis auratus, and in America probably of
Lachnosterna arcuata: G. echinodiscus lives in the
intestine of ant-eaters: G. spira in that of the
Fig. 4.
A, The larva of Echinorhynchus proteus from the body cavity of
Phoxinus laevis, with the proboscis retracted and the whole still
enclosed in a capsule.
B, A section through the same; a, the invaginated proboscis;
b, proboscis sheath; c, beginning of the neck; d,
lemniscus. Highly
magnified (both from Hamann).
king vulture, Sarcorhampus papa, and G.
taeniodes in Dicholopus cristatus, a cariama.
(iii.) Fam. Neorhynchidae. Sexually mature whilst still
in the larval stage. Neorhynchus clavaeceps in Cyprinus
carpio has its larval form in the larva of Sialis
lularia and in the leech Nephelis octcculii: tact
K. agilis is found in Mugil auratus and M. cephalus.
(iv.) Apororhynchidae. With no proboscis. This family contains
the single species Apororhynchus hemignathi, found near
the anus of Hemignathiis procerus, a Sandwich Island bird.
Fig. 5. -- Fully formed larva of Echinorhynchus
proteus from the body cavity of Phoxinus laevis
(from Hamann). Highly magnified. a, Proboscis;
b, bulla; c, neck; d, trunk; e, e, lemnisci.
AUTHORITIES. - O. Hamann, O. Jen. Zeitschr. xxv., 1891,
p. 113; Zool. Anz. xv., 1892, 195; J. Kaiser, Bibl.
Zool. ii., 1893: A. E. Shipley, Quart. Journ. Micr.
Sci. Villot, Zool. Anz. viii., 1885, p. 19. (A. E. S.)
ACANTHUS (the Greek and Latin name for the plant, connected
with ake, a sharp point), a genus of plants belonging to
the natural order Acanthaceae. The species are natives of
the southern parts of Europe and the warmer parts of Asia and
Africa. The best-known is Acanthus mollis (brank-ursine, or
bears' breech), a common species throughout the Mediterranean
region, having large, deeply cut, hairy, shining leaves. Another
species, Acanthus spinosus, is so called from its spiny
heaves. They are bold, handsome plants, with stately spikes,
2 to 3 ft. high, of flowers with spiny bracts. A. mollis, A.
lalifolius and A. longifolius are broad-leaved species; A.
spinosus and A. spinosissimus have narrower, spiny toothed
leaves. In decoration, the acanthus was first reproduced in
metal, and subsequently carved in stone by the Greeks. It was
afterwards, with various changes, adopted in all succeeding
styles of architecture as a basis of ornamental decoration.
There are two types, that found in the Acanthus spinosus,
which was followed by the Greeks, and that in the Acanthus
mollis, which seems to have been preferred by the Romans.
ACAPULCO, a city and port of the state of Guerrero on
the Pacific coast of Mexico, 190 m. S.S.W. of the city
of Mexico, Pop. (1900) 4932. It is located on a deep,
semicircular bay, almost land-locked, easy of access, and
with so secure an anchorage that vessels can safely lie
alongside the rocks that fringe the shore. It is the best
harbour on the Pacific coast of Mexico, and it is a port
of Call for steamship lines running between Panama and San
Francisco. The town is built on a narrow strip of low
land, scarcely half a mile wide, between the shore line and
the lofty mountains that encircle the bay. There is great
natural beauty in the surroundings, but the mountains render
the town difficult of access from the interior, and give it
an exceptionally hot and unhealthy climate. The effort to
admit the cooling sea breezes by cutting through the mountains
a passage called the Abra de San Nicolas had some beneficial
effect. Acapulco was long the most important Mexican port
on the Pacific, and the only depot for the Spanish fleets
plying between Mexico and Spain's East Indian colonies from
1778 until the independence of Mexico, when this trade was
lost. The town has been chosen as the terminus for two railway
lines seeking a Pacific port--the Interoceanic and the Mexican
Central. The town suffered considerably from earthquakes in
July and August 1909. There are exports of hides, cedar and
fruit, and the adjacent district of Tabares produces cotton,
tobacco, cacao, sugar cane, Indian corn, beans and coffee.
ACARNANIA, a district of ancient Greece, bounded on
the W. by the Ionian Sea, on the N. by the Ambracian
Gulf, on the E. and S. by Mt. Thyamus and the Acholous.
The Echinades islands, off the S.W. coast, are gradually
being joined up to the mainland. Its most populous region
was the plain of the Acholous, commanded by the principal
town Stratus; communication with the coast was impeded by
mountain ridges and lagoons. Its people long continued in
semi-barbarism, having little intercourse with the rest of
Greece. In the 5th century B.C. with the aid of Athens
they subdued the Corinthian factories on their coast. In
391 they submitted to the Spartan king Agesilaus; in 371
they passed under Theban control. In the Hellenistic age
the Acarnanians were constantly assailed by their Aetolian
neighbours. On the advice of Cassander they made effective
their ancient cantonal league, apparently after the pattern of
Aetolla. In the 3rd century they obtained assistance from
the Illyrians, and formed a close alliance with Philip V. of
Macedonia, whom they supported in his Roman wars, their new
federal capital, Lencas, standing a siege in his interest.
For their sympathy with his successor Perseus they were
deprived of Lencas and required to send hostages to Rome
(167). The country was finally desolated by Augustus, who
drafted its inhabitants into Nicopoiis and Patrae. Acarnania
took a prominent part in the national uprising of 1821; it
is now joined with Aetolia as a nome. The sites of several
ancient towns in Acarnania are marked by well preserved
walls, especially those of Stratus, Oeniadae and Limnaea.
AUTHORITIES.-Strabo vii. 7, x. 2; Thucydides; Polybius iv.
40; Livy xxxiii. 16-17; Corpus Inscr. Graecarum, no. 1739; E.
Oberhummer, Akarnanien im Altertum (Munich, 1887); Heuzey, Mt.
Olympe et l'Acarnanie (Paris, 1860). (M. O. B. C.; E. GR.)
ACARUS (from Gr. akari, a mite), a genus of
Arachnids, represented by the cheese mite and other forms.
ACASTUS, in Greek legend, the son of Pohas, king of Iolcus in
Thessaly (Ovid, Metam. vili. 306; Apollonius Rhodius i. 224;
Pindar, Nemea, iv. 54, v. 26). He was a great friend of Jason,
and took part in the Calydonian boar-hunt and the Argonautic
expedition. After his father's death he instituted splendid
funeral games in his honour, which were celebrated by artists
and poets, such as Stesichorus. His wife Astydameia (called
Hippolyte in Horace, Odes, iii. 7. 17) fell in love with
Peleus (q.v.), who had taken refuge at Iolcus, but when her
advances were rejected accused him falsely to her husband.
Acastus, to avenge his fancied wrongs, left Peleus asleep
on Mount Pellon, having first hidden his famous sword. On
awaking, Peleus was attacked by the Centaurs, but saved by
Cheiron. Having re-covered his sword he returned to Iolcus
and slew Acastus and Astydameia. Acastus was represented
with his famous horses in the painting of the Argonautic
expedition by Micon in the temple of the Dioscuri at Athens.
ACATALEPSY (Gr. a-, privative, and katalambanein, to
seize), a term used in Scepticism to denote incomprehensibility.
ACAULESCENT (Lat. acaulescens, becoming stemless, from a,
not, and caulis, a stem), a term used of a plant apparently
stemless, as dandelion, the stem being almost suppressed.
ACCA LARENTIA (not Laurentia), in Roman legend, the
wife of the shepherd Faustulus, who saved the lives of the
twins Romulus and Remus after they had been thrown into the
Tiber. She had twelve sons, and on the death of one of them
Romulus took his place, and with the remaining eleven founded
the college of the Arval brothers (Fratres Arvales). The
tradition that Romulus and Remus were suckled by a wolf has
been explained by the suggestion that Larentia was called
lupa (``courtesan'', literally ``she-wolf'') on account
of her immoral character (Livy i. 4; Ovid, Fasti, iii.
55). According to another account, Larentia was a beautiful
