260 
hydrographical conditions and the fauna being quite Atlantic, but 
the main point is that the species has spread very far towards both 
Polar areas (see the Addenda). Every deep sea organism spreading 
northwards in the Atlantic will meet the submarine ridge between 
Scotland, the Faeroes, Iceland, Greenland and Baffins Land; only 
between Iceland and Greenland will there be any probability of it 
penetrating into the true arctic deep, and if P. Haeckelii is identical 
with P. rubrum, this species has really happened to do so; if not, 
then in every case, the species in question demonstrates the possi- 
bility of spreading from the tropical oceanic depths towards both 
poles of the earth; it is not easy to comprehend, why such 
spreading should be impossible, ås the hydrographical conditions 
are nearly the same in every region of the Oceanic depths as far 
as the deep area extends without being limited by lands and sub- 
marine ridges”), Only comparatively few examples of this mode of 
distribution seem to be known with certainty, P. rubrum being the 
first indubitable example among the medusæ. But it must be re- 
membered that our knowledge of the fauna of the Oceanic depths is 
still very insufficient. The deep sea investigations of the "”Tjalfe” in 
the Davis Strait seem to me to be of great importance in this respect. 
List of Stations, where Medusæ have been captured. 
N 0. OP IN Far | W. Depth in | Apparatus Length of De Hour 
Station Long. meters us wire (meters) | Re 
la | 599 25' | 229 56' Young-fish 175 12,-5. 1908 8 p.m. 
trawl 
6 589 24" | 349 58' Ringtrawl (Surface) | 16.-5. » Hi pm 
9 589 88' | 859% 55' ” 600 SR OA 1 pm 
18 589 98" | 399 10' Young-fish 40 26.-5. » 8 p.m. 
trawl 
14 58? 08' | 899 12' Ringtrawl 150 26.-5. » 9 pm 
15 589 08" | 89924" ” EGE. da 1089 p.m. 
80a | 682 04' | 56932" ” 500 SØ. 8 kg pm 
33b | 689 25' 540 86 ” 200 8.-6. mr 10 am 
1) Compare Ortmann's and Chun's hypothesis, that the Arctic, the 
Antarctic and the oceanic depths make one special zoogeographical area. 
