= 
92 
NATURE 
Ss «ais 
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[Wov. 23, 1882 
2. Formicand acetic acids are to be regarded as constant pro- 
ducts of metastasis in vegetable protoplasm. 3. It is probable 
that other members also of the unstable group of fatty acids, as 
for instance, proprionic acid, butyric acid, caproic acid, or even 
the whole group, are universally distributed in the vegetable 
kingdom. 4. An increase of the amount of unstable acids takes 
place in a plant-organism when its assimilation is interfered with 
by deprivation of light, ze. when put into a state of starvation 
(inanition). 5. Formicand acetic acids accordingly belong to the 
constituents of regressive ti:sue-metamorphosis. It has been 
premised that the homologous, unstable fatty acids have a simi- 
lar import in-vegetable tissue-metamorphosis, 6. No increase in 
the amount of unstable acids takes place in a plant-organism, 
which is withdrawn for a period from the light, under the 
minimum-temperature required for growth. 7. Accordingly 
the formation of formic and acetic acids in a plant seems to take 
place -to a certain degree independently of respiration. 8. 
Acetic and formic acids are mainly to be regarded as decom- 
position products of the constituents of vegetable protoplasm. 
GEOGRAPHICAL NOTES 
Dr. WISSMANN, of the German African Society has, it 
is stated, just arrived at Zanzibar, having left Loando in 
April, 1881, in company with Dr. Pogge. Striking in- 
wards across the numerous streams that take their origin in 
the great watershed which separates the Congo and Zambesi 
basins, the travellers were at Mukenge, about 6° S. and 22° E., 
in November last year, Shortly after they set oui for Nyangwe 
on the Lualaba, whence Wissmann proceeded eastwards to Zan- 
zibar, while Pogge turned back to Mukenge, there to plant a 
station. The details of this journey will doubtless be full of 
novelty and interest. 
THe German African Society has recently issued a report 
upon its latest undertakings. There are now four German ex- 
peditions in Africa, two proceeding from the east, and two 
from the west. In the east there is Dr. Stecker, who as the 
companion of Dr. Rohlfs, paid a visit to King John of 
Abyssinia, and then continued his journey through the Soudan. 
His last letter is dated February 15. Dr. Béhrn aud Dr. 
Kayser, who belong to Capt. von Schéler’s expedition, report 
upon a three months’ journey to Lake Tanganyika, from which 
they returned to the station at the end of 1881. 
Gondo Station itself Herr Paul Reichard, who remained there, 
sends a report; Capt. v. Scholer, after founding a station at 
Kakama, proceeded to Zanzibar. News has also been received 
regarding the exploration of the Wala River, to the west of 
Gondo, as far as its mouth, by Dr. BGhrnand Herr Reichard. On 
the other hand, Robert Flegel is busily at work. He has taken 
a minute cartographical survey of the hitherto unknown part of 
the Niger, between Inuri and Shay. In the spring of 1881 he 
prepared for a journey to Southern Adanana. 
Keffi at the beginning of December; thence he intended to 
proceed by way of Schiber, on the Binne River, through the 
‘heathen lands” to Kantscha and Yola, south of the Binne, 
then winter there, and thence proceed by water from Meo Kebbi 
to the Tubori Marsh to Kuka. 
AT the beginning of November, Dr. Arthur Krause returned 
to Germany from his journey to the Chukchi Peninsula and 
Alaska, which he undertook, partly in company with his brother, 
Dr. Aurel Krause, and partly alone, at the instance of the Bre- 
men Geographical Society. Dr. Aurel Krause returned to 
Germany last summer by way of Panama, while his brother 
remained in Alaska until the autumn. The two brothers have 
made copious collections of natural history and ethnographical 
specimens. 
THE November number of Petermann’s Mittheilungen contains 
an account by Dr. Gerhard Rholfs of the results of his recent 
journey in Abyssinia. Dr. Ferd. Léwl, of Prag, has a long and 
able paper on the origin of transverse-valleys ; Lieut. Kreitner 
describes the route from Ansifan through the Gobi desert to 
Hami; while there are interesting letters from Emin-Bey, 
Lupton-Bey, and Dr. Junker, mainly referring to the work of 
the Russian explorer in the Welle region. He has been doing 
much to clear up the hydrography of the region, and has come to 
the conclusion that the Welle is really the upper course of the 
From the | 
| 
A SPECIAL supplement to the Chaméer of Commerce Fournal 
contains an account by Mr. Colquhoun of his recent journey 
through Yunnan to Burmah, accompanied by an excellent map. 
Under the title of ‘f Across Chrysé,” Messrs. Sampson Low and 
Co. will shortly publish a detailed narrative, with many illus- 
trations, of Mr. Colquhoun’s journey. 
THE ordnance survey of Scotland, a work which has been 
going on for thirty-seven years, has been completed, and the 
surveying staff will be withdrawn from Scotland next week. 
During the la:t few years nearly a hundred men have been 
employed in the work. 
THE Emperor of Russia has ordered 22c0/. to be allotted 
from the Imperial Treasury to the Russian traveller in New 
Guinea and the Malay Archipelago, M. Miklucho Maklay, in 
order to enable him to work up the results of his explorations. 
His Majesty has also ordered M. Maklay to be informed that 
the cost of the publication of his book of travels will be defrayed 
by the privy purse. 
THE PELAGIC FAUNA OF FRESHWATER 
LAKES 
SEVERAL naturalists have within recent years made the 
pelagic fauna of freshwater lakes in various regions a sub- 
ject of study. In the Archives des Sciences for September, Prof. 
| Forel gives a list of those researches, with a résumé of the 
results they have yielded. 
This fauna has but few species; but the number of indi- 
viduals of each species is, on the otber hand, enormous. The 
following is an enumeration of the species observed :— 
OsTRACODA: Cyfris cvum. CLADOCERA: Sida crystallina, 
Daphnella brachyura, D. pulex, D. magna, D. longispina, D. 
hyalina, D. cristata, D. galeata, D. quadranguia, D. mucronata, 
Bosmina longirostris, B. longispina, B. longicornis, Bythotrephes 
longmanus, Leptodora hyalina, COPEPODA: Cyclops coronatus, 
C. quadricornis, C. serrulatus, C. tenuicornis, C. brevicornis, 
C. minutus, Heterocope robusta, Diaptomus castor, D. gracilis, 
The author excludes from consideration those animals that 
enter into the pelagic fauna in an accidental and accessory way, 
such as fishes (especiaily Coregonus), preying on the entomos- 
traca, and other fishes which prey on those, also infusoria living 
on pelagic alge, and animals coming occasionally from the 
border or the bottom of a lake. 
The pelagic fauna is, in its general /vazts, very much the same 
in all European lakes where it has been examined, from the 
plains to the Alps, from Scandinavia to Italy. But it is rarely 
represented in one lake by all animals of the fauna. Pavesi has 
made a very complete study, in this respect, of the Italian Jakes, 
| giving, for each, a complete list of the species found. But an 
observation by Weissmann has to be remembered here. He 
| found that the different species of Cladocera presented an annual 
He reached | 
periodicity ; they disappear at certain seasons (different for 
different species), when they are represented only by eggs. Thus 
| the list of pelagic animals of a lake, to be complete, must be 
based on numerous takes in different seasons. 
The common characters of the fauna accord with the mode of 
life, which involves constant swimming ; thus the animals have 
no organ of fixation, but a well-developed organ of natation. 
Their density, nearly equal to that of water, enables them to 
float between two waters without exerting themselves much. 
Their movements are slow, and they escape enemies rather by 
their transparence than by agility. This transparence is, indeed, 
their essential character; they do not generally show a visible 
| point, except that of their eye, which is strongly pigmented with 
Shari, while the Aruwimi, the great tributary of the Congo, | 
rises further to the east. 
black, brown, or red. The quality of transparence may be 
interpreted as a case of mimicry. 
The food of the fauna is vegetable or animal. Some feed on 
pelagic alge, few in species, dnatana circinalis, Pleurococcus 
angulosus, Pl. palustris, Tetraspora virescens, Palmelia Ralfsiz, 
but very abundant in individuals; others pursue and eat the 
smallest animal species living in the same waters. 
The. pelagic animals present daily migrations ; swimming near 
the surface at night, and remaining in the depths by day. Fric 
thought he found, in the Bokemian lakes, each species select a 
determinate depth; neither Pavesi nor the author have observed 
such constancy. The different species form groups, or troops, 
where the net makes rich captures, but these banks of animals 
of the same species, have not, at least in the large Swiss lakes, 
a determinate fixed position, 
