140 EXPEDITION OF THE "ALBATROSS," 1899-1900. 



region of the Japan current north of the Ladrones the water teemed with 

 life, and the display of phosphorescence at night was truly remarkable. In 

 fact it is evident that pelagic animals are not abundant in regions far from 

 large land masses or where there are no well defined oceanic currents or 

 counter currents. As soon as one approaches the region of great currents 

 or counter currents, or the coasts of continents and larger islands, the number 

 of animals increases with remarkable suddenness. 



It was very noticeable that during the daylight hours our surface tows 

 were generally deficient in animal life, while those made at the same time 

 with an open net at depths varying between 300 fathoms and the surface 

 were remarkably rich both in number and variety of the specimens 

 obtained. It is evident that in the regions we examined the pelagic 

 animals sink to an unknown depth during the daytime. It should also be 

 noted that these same animals rise to the surface during the night, for our 

 surface hauls made at night were almost without exception much more suc- 

 cessful than those made in the same locality during the day. 



Among the twenty Hydromedusas obtained by the " Albatross," seven are 

 Trachylina and thirteen Leptolina forms. The relatively great number of 

 the Trachylina forms is quite striking, for these medusae are rare in waters 

 adjacent to the coasts of continents. In the open sea, however, they 

 constituted the greater number of the pelagic types. Our hauls in the 

 free expanse of ocean between California and the Marquesas were wonder- 

 fully rich in such Trachylina forms as Rhopolonema, Aglaura, and Liriope, 

 while yEgina and Solinaris were met with occasionally. Almost all of the 

 Leptolina forms were captured near some coast or among the islands of an 

 archipelago. There were, however, two remarkable exceptions to this 

 rule : A young Sarsia was obtained in N. Lat. 9° 45', W. Long. 137° 47', 

 where the nearest land (the Marquesas) was more than 1000 miles away ; 

 and a Tiara was found 600 miles north of the Marquesas. In general, how- 

 ever, the results support the conclusions of Maas, 1 in the case of the Plankton 

 Expedition, that Leptolina forms are creatures of the shallower waters near 

 coasts, while the Trachjdina are animals of the open ocean. 



1 Maas, O., 1893; Craspedoten Medusen der Plankton-Expedition. Also On some Problems of the 

 Distribution of Marine Animals, Natural Science, London, Vol. II., p. 02—99. 



