PLANKTONIC. STUDIES. 575 
The excursion to the coral reefS of the Red Sea (1875), which is 
recounted in my ‘“‘ Arabie Corals,” and the trip to Ceylon, about which 
I have written in my “Indian Journal” (Jndische Reisebriefe, 1882), 
were extremely valuable to me, because [ thereby gained an insight 
into the wonders of the Indian fauna and flora. On the journey from 
Suez to Bombay (in November, 1881), as well as on the return from 
Colombo to Aden (in March, 1882), I was able to make interesting 
observations on the pelagic fauna of the Indian Ocean, as well as dur-_ 
ing a six weeks’ stay at Belligam and in the pelagic excursions which 
I made from there. I obtained thereby a living picture of the oceanic 
and neritic fauna of the Indo-Pacific region, which differs in so many 
respects from that of the Atlantic-Mediterranean region. The special 
results of my experience there are, with the kind consent of Dr. John 
Murray, for the most part embraced in my report on the Radiolaria 
(1887), and on the Siphonophora (1888), which form parts XvuII and 
Xxvill of the Challenger Report. These two monographic reports also 
contain many observations on plankton, which I had made in earlier 
journeys and had not yet published. 
The extensive experience which I had gained through my own obser- 
vations of living plankton during a period of three decades was well 
filled out by the investigation of the large and well-preserved planktonic 
collections placed at my disposal from two different sources by Capt. 
Heinrich Rabbe, of Bremen, and by the Challenger directors of Edin- 
burgh. Capt. Rabbe, with very great liberality, turned over to me the 
valuable collection of pelagic animals which he had obtained on three 
different trips (with the ship Joseph Haydn, of Bremen) in the Atlantic, 
Indian, and Pacific oceans, and which he had carefully preserved 
according to my directions and by approved methods. This extraor- 
dinarily rich and valuable material, contained in numerous bottles, 
embraced planktonic samples from the most diverse localities of the 
three oceans, chiefly in the southern hemisphere. Like the much more 
extensive collection of the Challenger, it gives (though to a smaller 
degree) a complete summary of the complexity of the composition of the 
plankton and the difference. in its constituents. Rabbe’s collection 
supplements that of the Challenger in a most welcome manner, since the 
course of the Challenger was southward from the Indian Ocean through 
the Antarctic region, and between the Cape of Good Hope and Mel- 
bourne was always south of 40° south latitude. The course of the Joseph 
Haydn, on the other hand, on the repeated voyages through the Indian 
Ocean, was much more northerly, and between Madagascar, the Cocos 
Islands, and Sumatra included a number of points where the pelagic 
net obtained a very rich and peculiarly constituted capture. I hope 
to be able to publish soon in detail the special results which I have 
obtained by investigation of Rabbe’s plankton collection, with the aid 
of the carefully kept journal which Capt. Rabbe made of his observa- 
tions. The discoveries of new radiolaria, meduse, and siphonophores 
