TAQ ZOOLOGICAL 
test or cell, but usually the whole of the test is 
calcified, with the exception of the aperture 
through which the tentacles are extruded. In 
the largest group (Chilostomes), the aperture is 
guarded by a membranous, hinged operculum 
which is shut down like a trap door when the 
animal is retracted. In another group (Ctenos- 
tomes), a circle of bristles guards the aperture. 
For the protection of the colony, a majority 
of the Chilostomes have developed peculiar or- 
gans known as avicularia and vibracula. These 
structures are really highly modified individuals 
which have undergone great changes, both func- 
tionally and structurally, and have lost by degen- 
eration all the internal organs except the muscles 
of the operculum, which are greatly hypertro- 
phied. In the case of the avicularium the oper- 
culum has become modified into a beak-like or- 
gan, and in the vibraculum the process is carried 
still farther so that the beak becomes a long 
lash-like organ. ‘These organs are kept in 
motion snapping or lashing back and forth to 
prevent other forms from taking up their abode 
on the surface of the colony. ‘There is good 
evidence to show the evolution of the avicular- 
ium from the ordinary individual. ‘The struct- 
ure obtained its name from the fact that in 
certain genera (Bugula, Bicellaria) it is shaped 
like the head of a bird and mounted on a neck- 
like stalk. This is a highly modified condition, 
however, and the simplest type is found sessile 
between other cells of the colony and scarcely 
distinguishable from them except in the size of 
the beak. Spines and protuberances are also 
of frequent occurrence in the Bryozoa and aid 
in protection. 
The presence of sexual reproduction has al- 
ready been mentioned. The eggs are developed 
in the spacious body cavity and in some forms 
are retained there until ready to be liberated as 
free-swimming larvae. In other cases a special 
brood-sae or ovicell is formed to harbor the em- 
bryos until ready to be released. There are two 
quite distinct types of ovicell, according to their 
manner of formation. In the group of Cyclos- 
tomes one or more individuals of the colony be- 
come especially modified to serve as a brood- 
chamber for the colony. In the Chilostomes, on 
the other hand, a special organ may be formed 
by each fertile individual. The eggs migrate into 
this pouch and undergo their later development 
there. The ovicells are very characteristic of 
the different species, and when present they 
offer one of the best means of identification. 
The development of brood-chambers serving the 
same physiological purpose but of different 
origin affords a splendid example of the power 
SOCIETY 
BULLETIN. 
of functional adaptation in 
parallel evolution. 
The number of species of these interesting 
animals to be found in the immediate vicinity of 
New York City has not been determined. More 
than eighty species have been taken by the 
writer within a short distance of Woods Hole, 
Mass. Probably the number about New York 
City is considerably less than this, as most of 
the species require purer sea water than our 
harbor affords. Several species have been suc- 
cessfully kept in the Aquarium and some of 
these have attracted considerable attention when 
exhibited enlarged a few diameters in the lens- 
exhibit aquaria. R. C. O. 
bringing about 
THE FRESHWATER EEL. 
HE breeding habits of the eel, until very re- 
cent years, have always been a mystery to 
the naturalist as well as the angler. The 
ancients believed that eels were generated spon- 
taneously from the mud, while among fishermen 
the notion is still prevalent, in some places, that 
eels are the males of catfish. Such superstitions 
as the above arose naturally in the attempt to 
explain the absence of eels with spawn in streams 
or ponds where the species may abound—and 
of course mud and catfish are abundant every- 
where; and although naturalists have known 
that the eels must breed normally like other 
fishes, yet how, when and where? 
The first step toward clearing up these ques- 
tions was made by Dr. Theodore Gill’s sugges- 
tion nearly fifty years ago (1864), that the 
ribbon-like, pelagic fish known as the Leptoce- 
phalus is the larva of the Conger eel. This was 
later proved to be true (1885), when Delage 
succeeded in rearing the Conger eel through its 
metamorphosis from the Leptocephalus. 
The metamorphosis of the common European 
eel, (Anguilla vulgaris), was discovered in 1897, 
by two Italian zoologists, who proved that the 
larva known as Leptocephalus brevirostris de- 
velops into the elver or young eel of this species. 
This study was made in the Straits of Messina 
at the point where Charybdis, the fabulous 
daughter of Poseidon, was supposed by the an- 
cients to draw ships to their destruction in the 
depths of a whirlpool. In the currents at this 
point many abyssal animals are brought to the 
surface, and among these were obtained the 
leptocephali of the European eel. 
Extensive studies carried on in recent years 
by Dr. Joh. Schmidt for the Danish government 
have brought to light the following remarkable 
facts: (1), the fresh water eel must return to the 
