NATURE 
[SEPTEMBER II, 1913 
54 
| 
Temperature Rainfall Sunshine 
—— : ————awv\>—anaa | 
1913 lee le || ie /$. S ime Eo 
geleejgctes) gifgieeie| @ jee) § |) ee 
r si. & 2 bil eee 14 ri 
adleteges 2 egies 2) & ef] e jes 
218 | sR ENG pe la" ae 
. ° = Fea ot In. |. In. | 
June pera o|«o] o 61r| o | 12 8 | o'6r | -2°33] 204 || +22 
July -| 68 |-6 | 52 |=1 | 60 |-4!} 1 | x2] 2’%0r +0'12| 95 -9g1 
August ...) 71 |—2 | 52 |—1 | 62 |~1 | g | ax | 2°07 |-0'27| 143 | —34 
Summer...| 70 |-3 | sx |-1 | 6x |-2 | 22 | 31 ) 4°60 |- 1°45] 442 |- 103, 
It is seen that June was very dry, but in other 
respects fairly normal. July had a fairly normal 
rainfall, but only about one-half of the average sun- 
shine, whilst the temperature was exceptionally low. 
August was very dry until quite the close of the 
month, when exceptionally heavy rains fell over the 
south-eastern portion of England; at Greenwich the 
total for the last three days of the month was 1-22 in. ; 
both sunshine and temperature were deficient. 
Cuas. Harp1nc. 
A MEMOIR ON THE ARTHROPOD EYE.) 
eee progress has been made of late 
towards the elucidation of the structure of the 
arthropod eye. Prof. G. H. Parker, of Harvard, 
was the first seriously to attack the more intricate 
problems of its structure, and his insight was such 
that most of his work stands unchanged even after 
the more recent elaborate researches of Hesse, 
Schneider, and others. In the present paper Dr. 
‘lrojan has, in addition to his own researches, verified 
or corrected the observations of these later investiga- 
tors, whose work had summarised and illuminated the 
results of earlier writers. 
It will be of profit to mention briefly the interesting 
points that Dr. Trojan has been able to add to our 
knowledge. The corneal cells are not ‘ tile-shaped,” 
but they are broader distally than proximally, so that 
they appear triangular in transverse section. The 
author is unable to support Schneider’s observation 
that they are four in number, but agrees with Parker 
and Hesse that there are only two. The structure of 
the crystalline cells (cone cells) differs in one respect 
from that described by other writers; the upper part, 
the “‘ Zapfen,”’ is abruptly cone-shaped distally, and 
passes between the corneal cells to the facet. The 
general structure of the retinular cells and rhabdome 
is as Parker and later writers have described, but Dr. 
Trojan supports Hesse’s opinion (and differs from 
Parker and Schneider) that there is no ‘‘zwischen- 
substanz”’ (matrix) between the ‘‘ stiftchen "’ (fine rods) 
composing each half-plate of the rhabdome. The in- 
nervation of the rhabdome is effected as Hesse 
described, the nerve fibrilla passing up the outer side 
of the retinular cell, round the nucleus, and terminat- 
ing on ‘‘knépfchen”’ as the base of the “ stiftchen”’ 
composing the lamella of the rhabdome. Three optic 
ganglia are described. 
The most important part of the paper is devoted 
to a study of the pigment of the eye in darkness and 
light; this, however, is best consulted in the original. 
There are only two pigment-bearing cells which form 
a continuous tubular sheath enclosing the whole 
ommatidium from the crystalline cones to the bundles 
of nerve fibrilla under the basement membrane. The 
author’s observations on the movements of the pig- 
ments of these cells, and also of the non-pigmented 
tapetum cells are of considerable interest. 
In the course of the paper Dr. Trojan deals suc- 
cessively, under separate headings, with the different 
1 “Das Auge von Palaemon Squilla." By Dr. E. Trojan. Denk. d. 
Kais. Akad. d. Wiss. math-naturw. Klasse. Bd. 88. Wien, 1912. 54 pp. +6 pl. 
NO. 2289, VOL. 92] 
elements of the eye, giving an exhaustive anatomical 
and historical account of each, an arrangement which 
is lucid and very easy to follow. The plates illustrat- 
ing the paper are very fine—we wish we could believe 
they could have been as exqtisitely reproduced in 
this country—though we should have preferred to have 
had more of the author’s own drawings in place of 
the photographs, beautiful as they are. 
Dr. Trojan’s paper is an important contribution to 
the literature of the arthropod eye, not only for the 
original matter it contains, but also as a critical 
review of the work of previous observers. 
H. (Ga 
BIOLOGY OF AQUATIC PLANTS: 
R. W. H. BROWN has contributed an important 
paper on the biology of aquatic flowering plants 
to The Philippine Journal of Science (vol. viii., 
pp. 1-20), under the title, ‘‘ The Relation of the Sub- 
stratum to the Growth of Elodea.”” He confirms the 
statements ot previous observers that in this and in ~ 
other submerged plants there is a ‘‘ transpiration cur- 
rent’’ of water up the vessels of the stem, but his 
experiments lead to the conclusions that this current 
is simply a necessary consequence of the physical con- 
struction of the plant, and that the passage of water 
through a submerged plant does not show that the 
movement is of advantage to the plant by causing 
condensation of nutrient salts or that the roots are 
of advantage as absorbing organs. 
Dr. Brown gives tables showing the relative growth 
of Elodea with and without addition of carbon dioxide 
to the water, in tap water, and in Knop’s solution, with 
and without soil, rooted in and simply anchored over | 
soilor sand, &c., and summarises the results as follows. 
Sufficient carbon dioxide to keep Elodea growing or 
even alive does not diffuse from the air into the water 
during winter and spring; the substratum probably 
serves as an important source of this gas. Elodea 
is not dependent on its roots for absorption of mineral 
salts, the chief function of the roots being to anchor 
the plant to the soil, which is advantageous when 
the soil contains organic matter and gives off carbon 
dioxide; plants rooted in good soil grow better than 
those anchored over the same soil. When carbon 
dioxide was supplied by a generator instead of by the 
soil, rooted and anchored plants grew about equally 
well; with similar soils, and no external supply of 
carbon dioxide, floating plants grew better than rooted 
ones, the air being in this case the source of carbon 
dioxide. 
The author’s work is of great interest with refer- 
ence to the relation between the growth and abund- 
ance of plankton organisms (which form a large pro- 
portion of the food of fishes) and of larger water 
plants, and has obvious economic bearings; for in- 
stance, his experiments would seem to show that the 
larger submerged plants compete with the plankton 
algz for both carbon dioxide and mineral salts, and 
must therefore be detrimental to their growth. 
. 
UNIVERSITY AND. EDUCATIONAL 
INTELLIGENCE. 
Lonpon.—A course of twelve post-graduate lectures 
on “Conductors for the Electrical Transmission of 
Energy” will be delivered at University College by 
Prof. J. A. Fleming, F.R.S., beginning on October 29. 
The course, which is intended for post-graduate 
students and for telegraphic and electrical engineers, 
engaged in practical work, will be divided into two 
parts, which may be attended separately. Part i. will 
