CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 47 
terranean, and it is evidently distributed entirely across the tropical 
Atlantic, being fairly common at times at Tortugas, Florida. 
The animal moves by vermiform contractions, aided by its combs 
of cilia, and advances with remarkable rapidity by a series of sudden 
darts with intervals of rest between. I have seen a perfect specimen of 
this ctenophore which was swimming normally in an aquarium suddenly 
tear itself into shreds through muscular contraction. 
Order BEROIDZ Eschscholtz, 1820. 
Beroide, EscHscHoLtz, 1829, Syst. der Acal., p. 35.-GEGENBAUR, 1856, Archiv 
fiir Naturgesch., Jahrg. 22, p. 192.—Acassiz, A., 1865, North Amer. Acal., 
Pp. 35.—CuHuN, 1880, Ctenophoren des Golfes von Neapel, p. 303. — Moser, 
1903, Ctenophoren der Siboga-Exped., p. 19.—VANHOFFEN, 1906, Nordisches 
Plankton, Ctenophoren, p. 7.— ROMER, 1903, Fauna Arctica, Ctenophoren, 
Bd. 3, p. 81.— BENHAM, 1907, Trans. New Zealand Institute, vol. 39, p. 139. 
Agassiz regarded the Beroide as the simplest of the ctenophore 
and considered that the more complexly organized Lobate, Cydippide, 
and Cestide were derived from them. They are simple in that they lack 
tentacles and tentacular canals. The structure of the apical sense- 
organ and the papille of the pole-plate are, however, more complex than 
in other orders of ctenophore. Chun, 1880 (pp. 267, 271), contrary to 
Agassiz, regards the Beroidez as the most highly differentiated of cteno- 
phore and considers that they have remotely descended from tentac- 
ulate forms, and that they can not be regarded as the ancestral type from 
which the existing tentaculate ctenophore have been derived. 
The loss of the tentacles in the Berodia may have come about, 
according to Chun, through the powerful development of the cilia, giving 
freedom and rapidity of motion, and through the great development of 
the wide-flaring mouth which enables the animal to obtain food without 
depending upon tentacles to capture prey. It is remarkable, however, 
that no trace of tentacles or tentacular vessels appears in the larve of 
Beroide, but we must remember that in the genus Ocyropsis of the 
Lobatz there are neither tentacles nor tentacular vessels, so that the case 
of the Beroide does not stand alone and need give us no great concern. 
Moreover, in essential respects the fusions between the oral branches of 
the paragastric and the meridional canals are similar in Cestide and 
Beroide excepting that in the Beroide an anastomosing network may 
connect some or all of the meridional canals one with another. 
The lateral diverticula of the meridional and oral branches of the 
paragastric canals, which are seen only in the Beroidz, are evidently, 
phylogenetically speaking, of recent origin, for they appear very late in 
ontogeny in Beroé. 
It is probable that the Beroidze and Cestidz are derived from a com- 
mon stock whose relationship to the Lobatz was close. 
The lateral compression in the funnel-axis is more marked in the 
Beroidz than in any other order of ctenophores excepting the Cestide. 
There are 2 genera, Beroé in which the aboral pole of the animal is 
dome-like and oval, and Nets Lesson, in which there are 2 prominent 
lobes on both sides of the apical sense-organ. (See von Lendenfeld, 
1885, Zeit. far wissen. Zool., Bd. 41, p. 673.) 
