CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 31 
1891 (Pfliger’s Archiv fur Physiol., Bd. 50, p. 423), concludes that the 
apical sense-organ in Beroé does not subserve the sense of hearing, but 
controls the orientation and equilibration of the animal. Without the 
sense-organ the animal assumes unnatural positions in the water. 
I find that the effective stroke of the cilia of Bolinopsis vitrea may 
sometimes be reversed by a solution composed of 0.625 molecular (100 
NaCl+11.6 MgCl,), so that the animal swims backward, 7.e., mouth-end 
forward. 
Mnemiopsis mccradyi Mayer. (Fig. 48, plate 8.) 
Mnemiopsis mccradyi, MAYER, 1900, Bull. Museum Comp. Zool. at Harvard Col- 
lege, vol. 37, p. 9, figs. 22, 23, plate 6. 
Fic. 9.—Mnemiopsis mccradyi, view of mouth, auricles, and oral lobes. 
au, auricle; dg, axial extension of paragastric canal; fg, oral forks 
of the paragastric canals; g, paragastric canal; m, mouth; mn, 
muscular net in the oral lobes; mst, meridional subtentacular 
combs; msv, meridional subventral combs; #, tentacular canal; 
ten, axial tentacle; tr, tentacular ridge. From life by the author. 
Port Royal, Jamaica, May, rgrt. 
The animal is about 100 mm. long, and the general form of the body 
is very similar to that of M. leidyt. The lateral compression of the body 
is, however, more marked, while the gelatinous substance is far more 
rigid and of a decided greenish-amber color and opalescent not trans- 
