
AUGUST 5, 1915 | 
NATURE 
629 


interferential methods to the study of the spectrum of 
the Orion nebula by Fabry, Buisson, and Bourget, 
work which, among many other interesting results, 
revealed the existence of the element of atomic weight 
3, previously predicted on theoretical grounds by Prof. 
Nicholson. 


MARINE BIOLOGY AT PLYMOUTH. 
N the latest number (vol. x., No. 4) of the Journal 
of the Marine Biological Association there are 
two papers of very considerable interest. Of these, 
the first deals with experiments in the rearing of 
plankton animals (Crustacean larvae and Copepoda) 
which are of importance as a food supply for fish. 
The authoris Mr. L. R. Crawshay. Plymouth Marine 
Station is justly celebrated for the invention by its 
director, Dr. Allen, of the method of rearing various 
types of marine larve by feeding them with pure 
cultures of the diatom Nitzschia. By this method the 
larvee of Echinodermata, Mollusca, and Annelida have 
been reared until they attained the adult condition. 
Mr. Crawshay has endeavoured to extend the method 
to Crustacea. He has made some interesting dis- 
coveries. Thus he finds that in spite of sterilised 
water and abundant food, Copepoda live a very short 
time unless the culture flask be kept cool and the tem- 
perature remains constant. Then he finds that the 
harmful action of bacteria has been much exaggerated. 
There are only one or two varieties which are fatal to 
Copepoda, but these are of infrequent occurrence. 
When he had arranged for a good food supply and a 
constant temperature, he was able to keep the delicate 
pelagic form, Calanus finmarchicus, alive for months, 
and to rear the nauplii of Pseudocalanus through 
all stages of development until the attainment of the 
adult condition. When this method has been per- 
fected it will be possible to study the life-histories of 
the economically important Copepoda in detail in the 
laboratory, instead of, as now, piecing the development 
together from scattered observations of plankton. 
The second paper to which we _ wish 
direct attention deals with twin larve of 
starfish Luidia. These larva developed from 
eggs which were artificially fertilised at Ply- 
mouth. When the eggs had attained the blastula 
stage they were sent in sea-water in a thermos flask 
to the author, Dr. Gemmill, lecturer in embryology 
in the University of Glasgow, by whom they were 
reared further. Dr. Gemmill ascribes the formation 
of twins to the shaking which the blastule endured 
on the journey from Plymouth to Glasgow; this seems 
to have caused partial rupture of the blastule at a 
time when the tissues are equipotential, and the 
partially separated fragments have each striven to 
produce a perfect larva. 
to 
the 
Besides these papers the volume contains a 
valuable list of the Annelida found in_ the 
neighbourhood of Plymouth by Dr. Allen. There 
is also a paper by Miss Olwen Rees, which we 
hope is the first of a series, which records the results 
of a systematic investigation of the internal anatomy 
of the British members of the Actinozoon family 
Sagartide. Too often accounts of the internal anatomy 
characteristic of a group have been founded on the 
dissection of a single “‘type”’ to the structure of which 
the other members have been assumed to conform. 
At a time when the war threatens the continued 
existence of such celebrated stations as Naples 
and Trieste, it is important to be reminded of 
the asset which British zoology possesses in the Ply- 
mouth Station, and of the necessity of making every 
effort to sustain it during this arduous time. 
E. W. M. 
NO. 2388. VOL. 95] 
| 
| 
| 
| siderable 
(mycologist) and by Mr. L. E. Campbell (rubber re- 

THE TAPPING OF RUBBER TREES. 
ie Ceylon Department of Agriculture has issued 
a number of circulars on the tapping of indi- 
vidual and groups of Hevea trees and the effect of 
such operations on the storage of plant food. All the 
experiments and observations are based on Hevea 
brasiliensis, most of the trees dealt with being of con- 
age. The papers are by Mr. T. Petch 
search chemist). 
The first circular gives the results obtained by 
tapping one old Hevea tree for four years and nine 
months. The tree was planted in 1877, and is sur- 
rounded with other trees of the same species. It is a 
tree of an unusual type in so far that the main stem 
branches into two at about 10 ft. from the ground. 
In a way it is a famous specimen, and has been much 
photographed in past years. In four years nine 
months this tree has given 392 lb. 7 oz. of dry rubber : 
a most phenomenal crop. The rubber was obtained 
from the original and renewed barlx on the basal por- 
tion of the stem. 
The other circulars dealing with Hevea tapping 
results cover two distinct periods; first from 1911 to 
1913 and second 1914. Experiments were made to 
determine the yield obtained by different frequencies 
of tapping and by different systems. Pricking and 
paring knives were also experimented with. The 
account of experiments for the period 1911-13 is 
largely statistical, very few deductions being drawn 
from the tabulated statements. The account of results 
for 1914 forms a continuation of those already referred 
to. While it would be too early to draw trustworthy 
practical conclusions from the results obtained, there 
are one or two points which become evident to the 
reader. They confirm previous results in so far that 
the yield per tapping increases as the time interval 
between consecutive operations is increased. The 
yield, however, in a given time is greatest with the 
more frequent tapping. It is further suggested that 
prolonged tapping on a single section, when cuts are 
2 ft. apart, has a detrimental effect on the yield. 
Reference is made to the fact now generally recog- 
nised that results of tapping experiments hitherto 
conducted are of little value because no count was 
taken of the varying capabilities of different tappers 
who do the work. In the circulars we now review 
this cause of variation was allowed for. 
Mr. Campbell’s circular on the effect of tapping on 
the storage of plant food in Hevea brasiliensis is ex- 
ceptional in character. In tapping operations the 
living cortex of the tree is cut away in order that the 
latex may freely exude. This destruction of living 
tissue is made good by rapid cambium activity which 
soon results in the production of a thiclk renewed 
cortex, except in those cases where the tappers have 
damaged the cambium. The renewed bark is con- 
ceived to be formed largely at the expense of reserve 
foods in the plant. Mr. Campbell has selected the 
starch grains as a reserve food, the fluctuation in 
quantity of which might indicate the varying effects of 
tapping operations. The author made a study of the 
bark of tapped areas, and by an ingenious method 
determined the number of starch grains in a given 
area. The work indicates that the effect of careful 
tapping is localised. This is not in accordance with 
the general view on the subject. The local effects: 
are especially apparent in a horizontal direction, and 
the author suggests that by changing tapping from 
one part of the tree to another at intervals the rest- 
ing period of each area so tapped is nearly as effective 
as if the whole tree were rested. The ‘change over” 
system is becoming quite common on a number of 
Ceylon estates. H. W. 
