MUSEUM OF COMPARATIVE ZOOLOGY. 87 
consists simply of a conical bag of muslin or buntine attached to an iron 
ring, is constantly open, — descending, dragging along, and ascending. 
If worked on the surface there is of course neither difficulty nor ques- 
tion, but if brought up from 500 fathoms, at which depth it has been 
towing for some time, the net may be supposed to contain chiefly the 
species living at that depth; but mixed with these there must be a con- 
siderable number of more superficial forms, some taken when the net 
was going down with its open mouth downwards, and many more cap- 
tured during its long ascent of halfa mile through the upper layers. 
We cannot therefore as yet say with certainty whether the surface 
species live in the deeper belts or not, but we are justified in concluding 
that species which are absent on the surface, and present only when 
a certain depth has been gained, are special to that and probably to 
greater depths, If again species differing both from those procured on 
the surface and at intermediate depths are found in the bottom deposits, 
it is a legitimate inference that these live below the zone of our deepest 
tow-net observations." ! 
The expedition of the * National" much as it has been ridiculed 
by Haeckel? and his champion, Carus Sterne? has done more to show 
that the pelagic fauna is a very scanty one to below 200 fathoms (400 
meters) than all the work of all the other explorers together, The ob- 
ject was to work up the “Plankton.” It is true it was not worked up 
according to Haeckelian methods,* but it has the immense advantage of 
being aceurate, and not being based either upon guesses or upon misrep- 
1 Challenger, Atlantic, Vol. I. p. 236. 
2 In his attack on Hensen's work, Haeckel constantly refers to the “ Ziele u. Wege 
der heutigen Entwiekelungsgeschichte," Jena, 1875. In the present diatribe, he 
has almost surpassed his former achievements. Such contemptible attempts to 
overwhelm one's opponents with ealumnies as are printed on pages 80 and 81 of 
the pamphlet referred to above are in accordance with his customary mode of 
argument. 
3 Rundschau, March, 1891. 
4 I quote from Hensen’s Die Plankton-Expedition und Haeckel’s Darwinismus, 
(p. 9): “Der Angriff auf die Expedition . . . kann vielleicht viel schaden, den er 
wird getragen von einer Autorität und wird begründet mit einer so grossen Anhäuf- 
ung von einseitig gedeuteten Thatsachen, dass jeder mit dén Verhältnissen nicht 
genau Vertraute davon überzeugt wird, dass die Plankton-Expedition vollig verfehlt 
sein müsse. Dennoch ist solehe ` eberzeugung nur auf Sand gebaut und steht in 
volligem Wiederspruch mit den Thatsachen ; und zwar nicht nur mit denjenigen, 
welche unsere Expedition nach weist, sondern, wie ich zeigen werde, selbst mit den 
Berichten, welche andere Expeditionen gegeben haben, sofern man dieselben nur 
richtig versteht." 
