CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 



31 



1891 (Pfliiger's Archiv fur Physiol., Bd. 50, p. 423), concludes that the 

 apical sense-organ in Beroe 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 (loa 

 NaCl-fii.6 MgClj), so that the animal swims backward, i>., 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. 



Fig. 9. — Mnemiopsis mccradyi, view of mouth, auricles, and oral lobes. 

 CM, 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 sub ventral combs; t, tentacular canal; 

 ten, axial tentacle; tr, tentacular ridge. From life by the author. 

 Port Royal, Jamaica, May, 19 11. 



The animal is about 100 mm. long, and the general form of the body 

 is very similar to that of M. leidyi. 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- 



