16 NATURE 
by the chronoscope, convince the authors that the 
inhibition or facilitation thus experimentally produced 
is one “which cannot be. . . explained neurologic- 
ally as a division of energy, or drainage.’ They be- 
lieve that ‘‘an association cannot be explained as a 
mere path of lowered resistance,” but that it ‘*in- 
volvgs other processes which prevent any other 
stimulus from using the same neuroses af the same 
time . . . and which block any other association that 
is tending to operate at the same time, even though 
both will lead to the same end result.” 
In vol. viii., Section D, No. 3. of The Philippine 
Journal of Science, Mr. A. E. W. Salt gives an 
elaborate account of the endowment provided by Fran- 
cisco de Carriedo y Peredo, the greatest benefactor of 
the city of Manila, who died in 1743. From the funds 
received under his will, a water supply was provided 
for the city until the American occupation. A new 
system to supplement the ancient supply was opened 
in 1908. Water is now brought from an almost 
virgin watershed of one hundred square miles in area, 
and thence carried to a storage reservoir with a 
capacity of 210,000,000 gallons. The city, however, 
is so rapidly developing that this system is barely 
adequate to the needs of the population. Mr. Salt 
has done good service in directing attention to the 
benevolence of a citizen who, at a time when sanita- 
tion occupied little public attention, devoted his wealth 
to this excellent purpose. 
In Professional Paper No. 79 of the United States 
Geological Survey, Mr. H. S. Williams discusses the 
recurrent Tropidoleptus zones of thé Upper Devonian 
in New York. In preparing the data for the Watkins 
Glen-Catatonk folio (No. 169 Geol. Atlas USUS, 
Geol. Survey, 1909) the occasional discovery of 
Tripodolpetus carinatus (Conrad) in strata far above 
the supposed range of the species or of the fauna with 
which the species is normally associated led the writer 
to undertake an examination of the sections and 
sequence of fauna where they appeared. The result 
throws important light upon the regional geography. 
The departure and return of the fauna must have 
been due to diastrophic changes which produced re- 
curring favourable or unfavourable conditions for the 
existence of the fauna. Those changes of conditions 
may have resulted from the alternate closing and 
reopening of an actual passage-way which obstructed 
or admitted the access of the fauna and of waters 
favourable to them, or from changes that affected 
the direction, character, or volume of the existing 
ocean currents. 
THe insect food of Canadian fresh-water fishes 
forms the subject of an article by Dr. Gordon Hewitt, 
the Dominion entomologist, published in the fourth 
annual report of the Commision of [Fish] Conservation 
of Ottawa. Attention is directed by the author to the 
futility of attempting to restock depleted rivers, or to 
introduce new kinds of fish into Canadian rivers, 
without taking measures to ensure an abundant supply 
of suitable insect food. In Europe it has been demon- 
strated that the artificial cultivation of many kinds of 
insects constituting ‘the chief food of fishes is per- 
practicable; and in many rivers an insect 
NO. 2288, VOL. 92] 
fectly 
[SEPTEMBER 4, 1913 
hatchery is almost as necessary and important as a 
fish-hatchery. Before such insectaria can be introduced 
with satisfactory results in Canada, a close investiga-_ 
tion into the nature of the food of native or intro- 
duced fishes is absolutely essential. 
A RECENT number of the Zeitschrift fiir wissen- 
schaftliche Zoologie (Bd. cv., Heft 3) is entirely de- 
voted to a memoir on the chemical composition of the 
hemolymph of insects and its significance as regards 
sexual differentiation. According to the author, Herr 
Kurt Geyer, the haemolymph in caterpillars and pup 
of Lepidoptera is usually green in females and pale 
yellow or colourless in males. The green pigment 
is, as Poulton has already shown, slightly altered 
chlorophyll in solution, derived from the food-plant ; 
it constitutes a protective coloration, and it is improb- 
able that it has any assimilatory function. The yellow 
colour of the male haemolymph is due to the yellow 
constituents of chlorophyll (xanthophyll). The hamo- 
lymph of non-phytophagous insects shows no such 
colour difference. When the male and female hemo- 
lymph are mixed a heavy precipitate is at once formed, 
and this reaction can only be distinguished quantita- 
tively from that which takes place between different 
species. The author concludes that in insects the 
entire soma is sexually differentiated in male and 
female. 
Dr. C. H. Ostenretp’s account of the biology and 
distribution of the phytoplankton of Danish seas (De 
Danske Farvandes Plankton i aarene 1898-1901. 
Phytoplankton og Protozoer. D. Kgl. Danske, 
Vidensk. Selsk. Skrifter. 7. Raekke, Naturvidensk 
og Mathem. Afd. ix. 2. 1913) is of more than local 
interest. The main work is written in the Danish 
language, but there is a résumé in French, extending 
to 65 pp., which in itself constitutes one of the best 
summary accounts which we possess of the present 
state of our knowledge of the general problems of 
the biology of plankton organisms. The Danish seas, 
extending as they do from the Baltic through the deep 
waters of the Skager Rak to the North Sea, furnish 
such wide variations in salinity, temperature, and 
chemical constitution, that they offer exceptional 
opportunities for studying the effects of physical con- 
ditions on the distribution of the plankton, and this 
aspect of the subject receives a full consideration in 
the report. A good bibliography will be found on 
Pp- 346-352. 
From the Kommissionen for Havundersogelser in 
Copenhagen we have received three further reports 
dealing with the investigations which have been 
carried out under the direction of Dr. Johs. Schmidt- 
into the life-histories of eels. These are: Danish re- 
searches in the Atlantic and Mediterranean on the 
life-history of the freshwater-eel (Anguilla vulgaris, 
Turt.), with notes on other species, by Johs. Schmidt 
(Internat. Revue Hydrobiologie und Hydrographie, 
1912); on the identification of murznoid larvee in their 
early (preleptocephaline) stages, by Johs. Schmidt 
(Meddel. Komm. Havunders. Fiskeri Bd. iv. 2); and 
the metamorphosis of elvers as influenced by outward 
conditions—some experiments, by A. Strubberg 
(Meddel. Komm. Havunders. Fiskeri Bd. iv. 3). In 
Narvre, vol. Ixxxix., pp. 633-636, Dr. Schmidt himself 
: 
