APRIL 30, 1914] 
NATURE 
EASTER VACATION WORK AT 
PORT “ERE 
~HE Easter vacation party at the Port Erin Bio- 
logical Station has this year been larger than 
ever before, and has carried out a longer programme 
of work—both in the laboratory and on the seashore. 
During the last few weeks (March and April) the 
number of researchers and senior students enrolled in 
the books of the station has reached the record total 
of eighty-five, including half a dozen professors and 
a dozen university lecturers and demonstrators, while 
nearly half of the total number were post-graduate 
researchers. Altogether twelve universities or univer- 
sity colleges have been represented. Practically all 
the senior students and post-graduate workers of the 
botanical and zoological departments of the Univer- 
sity of Liverpool, under Profs. Harvey Gibson and 
Herdman, migrated to the Port Erin laboratory for 
the vacation. Prof. Cole brought a considerable con- 
tingent from the University College of Reading, and 
Dr. Stuart Thomson a number from Manchester; Mr. 
Holden came with some students from University 
College, Nottingham, and smaller groups came from 
Birmingham, Cambridge, Oxford, Bristol, Bangor, 
Cardiff, London, and Meibourne. In addition to the 
laboratory work of the students and their collecting 
expeditions on the seashore, the activities of the bio- 
logical station at this time of year are threefold: 
first, the flat-fish hatching (seen at its best during 
March and April); secondly, the plankton investiga- 
tion going on at sea from the s.y. Runa; and thirdly, 
the special investigations of the post-graduate re- 
searchers. 
The spawning of the mature plaice in the open-air 
fish-ponds started at the beginning of February this 
year, at least a fortnight earlier than usual, and it is 
by no means finished yet. Already more than eight 
millions of eggs have been skimmed from the ponds, 
and about seven millions of young fish have been set 
free in the sea round the south end of the Isle of 
Man. 
Work at sea was much hampered by bad weather 
during the earlier part of the time, and it was some- 
times difficult to get the periodic plankton hauls taken. 
This is now the eighth year of Prof. Herdman’s 
scheme of intensive study of the nature and distribu- 
tion of the plankton, of which it is hoped to com- 
plete ten years’ statistics before winding up the inves- 
tigation. Up to the present the phytoplankton this 
spring has been characterised by the prevalence of 
Coscinodiscus. 
In addition to the collecting and recording of rare 
species, both of animals and sea-weeds, which has 
gone on very much as in former years, there has 
been a large amount of special investigation both at 
sea and in the laboratory on the part of those who 
are engaged in the preparation of L.M.B.C. Memoirs, 
and also of others who are at various researches. For 
example, Mr. R. D. Laurie has been making observa- 
tions on the movements of Amphidinium in the sand, 
Mr. S. T. Burfield has been working at Sagitta, Miss 
Gleave at Archidoris, Mr. H. G. Jackson on Decapod 
larve in the plankton, and Prof. B. Moore and Mr. 
E. Whitley on the nutrition of marine animals and 
the variations in the alkalinity of the sea-water. The 
memoir on Echinoderm larve which Mr. Chadwick 
has been engaged on for some years is now in the 
printer’s hands, and wili be published at an early 
date. The pressure on the laboratory accom- 
modation has been very great during this vacation, 
and the need of further extension of the building is 
urgent. 
Wr A. Ths 
NO. 2322, VOL. 93| 
227 
RELATIONS BETWEEN THE SPECTRA AND 
OTHER CHARACTERISTICS OF THE 
SS AWE Ses aes 
Ihe 
Historical. 
] NVESTIGATIONS into the nature of the stars 
must necessarily be very largely based upon the 
average characteristics of groups of stars selected in 
various ways—as by brightness, proper motion, and 
the like. The publication within the last few years 
of a great wealth oi accumulated observational mate- 
rial makes the compilation of such data an easy pro- 
cess; but some methods of grouping appear to bring 
out much more definite and interesting relations than 
others, and, of all the principles of division, that 
which separates the stars according to their spectral 
types has revealed the most remarkable differences, 
and those which most stimulate attempts at a 
theoretical explanation, 
In the present discussion, I shall attempt to review 
very rapidly the principal results reached by other 
investigators, and shall then ask your indulgence for 
an account of certain researches in which I have been 
engaged during the past few years. 
Thanks to the possibility of obtaining with the 
objective prism photographs of the spectra of hundreds 
of stars on a single plate, the number of, stars the 
spectra of which have been observed and classified 
now exceeds one hundred thousand, and probably as 
many more are within the reach of existing instru- 
ments. The vast majority of these spectra show only 
dark lines, indicating that absorption in the outer and 
least dense layers of the stellar atmospheres is the 
main cause of their production. Even if we could not 
identify a single line as arising from some known 
constituent of these atmospheres, we could nevertheless 
draw from a study of the spectra, considered merely 
as line-patterns, a conclusion of fundamental import- 
ance. 
The spectra of the stars show remarkably few 
radical differences in type. More than 99 per cent. of 
them fall into one or other of the six great groups 
which, during the classic work of the Harvard Col- 
lege Observatory, were recognised as of fundamental 
importance, and received as designations, by the pro- 
cess of ‘‘survival of the fittest,’’ the rather arbitrary 
series of letters B, A, F, G, K, and M. -That there 
should be so few types is noteworthy; but much more 
remarkable is the fact that they form a continuous 
series. Every degree of gradation, for example, be- 
tween the typical spectra denoted by B and A may 
be found in different stars, and the same is true to 
the end of the series, a fact recognised in the familiar 
decimal classification, in which Bs5, for example, 
denotes a spectrum half-way between the _ typical 
examples of B and A. This series is not merely con- 
tinuous; it is linear. There exist indeed slight differ- 
ences between the spectra of different stars of the 
same spectral class, such as AO; but these relate to 
minor details, which usually require a trained eye for 
their detection, while the difference between successive 
classes, such as A and F, are conspicuous to the 
novice. Almost all the stars of the small outstanding 
minority fall into three other classes, denoted by the 
letters O, N, and R. Of these O undoubtedly pre- 
cedes B at the head of the series, while R and N, 
which grade into one another, come probably at its 
other end, though in this case the transition stages, 
if they exist, are not yet clearly worked out. 
From these facts it may be concluded that the prin- 
* An address delivered before a joint meeting of the Astronomical and 
Astrophysical Society of America and Section A of the American Association 
for the Advancement of Science, at Atlanta, Georgia, December 30, 1913, 
with a few additions, by Prof. H. N, Rusrell. 
