124 
NATURE 
[JUNE 5, 1902 
disuse of the term ‘‘epipharynx,” “‘as it is really part of 
the upper lip.” This is not shown to be so if carefully 
prepared serial transverse sections are made of the 
proboscis. By this means it is seen that the epipharynx 
is a tunnel-shaped tube through which blood is drawn up 
and which is strengthened on each side by a chitinous 
rod, in the centre of which is a core of chitin-forming 
cells—prolongations forward of the cells lining the 
external chitin of the whole body. The epipharynx is 
by its dorsal surface very intimately connected with the 
“labrum,” or upper lip proper, throughout its whole 
length. That the labrum does not, however, extend as 
far as the tip of the epipharynx is shown by the presence 
of the core of chitin cells which here approaches the 
dorsal surface. The two pieces, the labrum and the 
epipharynx, therefore represent two distinct organs, 
which are bound closely together for a great part of their 
length by a delicate connective tissue, so that the com- 
bined organ might rather be called the “labrum- 
epipharynx,” a term first suggested by Dimmock. Near 
the base of the proboscis the labrum is composed of a 
curved lamella of chitin, concave upwards, convex 
towards the convex upper surface of the epipharynx—the 
open sides being closed by folds of delicate chitin, which 
unite below with the lateral rods of the epipharynx, the 
space thus enclosed being filled with delicate loose 
cellular connective tissue. 
Mr. Theobald also describes the hypopharynx as ‘‘a 
small needle-like thread connected with a poison gland 
at its base.” The hypopharynx does not lie between the 
four stylets (the mandibles and the maxillz) and the epi- 
pharynx, but, as is well shown in well-prepared sections, 
the lower edges of the mandibles fit in between the hypo- 
pharynx and the epipharynx at the sides, and only in 
the middle line do the thin lower edges of the epipharynx 
and the upper surface of the hypopharynx meet. More- 
over, the structure at the base of the hypopharynx is not 
a poison gland, but, a receptacle for the collection of 
veneno-saliva secreted by the salivary glands situated in 
the prothorax. This receptacle is somewhat trumpet- 
shaped, with sides of strong rigid chitin, The mouth 
opens on to the upper end of a groove which runs along 
the whole length of the hypopharynx, the veneno-salivary 
gutter ; whilst the broad end is composed of delicate 
membranous tissue, and receives about its middle the 
insertion of the common salivary duct. Into this mem- 
brane also are inserted the tendons of delicate muscles. 
The receptacle is simply a store for” saliva which is 
discharged by the falling back of the membrane, pre- 
viously retracted by the muscles attached to it. 
Mr. Theobald emphasises the importance of the scale 
structure of the insects, and considers it to be one of 
the most important characters for both generic and 
specific distinction ; the whole classification in the mono- 
graph is mainly based on the scale structure. In the 
description of the wings, the terminology of Skuse, 
which is the simplest and best suited for purposes of 
identification, has been adopted. 
The paragraphs on the bionomics of mosquitoestreat 
chiefly with the habits of Anopheles and Culex. “These 
paragraphs contain many incorrect and misleading 
statements, and other recent works might be consulted 
NO. 1701, VoL. 66] 
for more trustworthy information on this subject. For 
example, the author concludes that Anopheles maculi- 
Pennis does not bite here in England, and suggests the 
question whether this may not have some bearing on 
the dying out of malarial fever in this country. Now 
there is no doubt that A. maculipennis have been found 
gorged with blood in some parts of England in bedrooms 
and other places. Moreover, however closely the dis- 
tribution map of the English Anopheles corresponds 
with the old malarial district map which Dr. Nuttall has 
worked out, it is quite certain that there is hardly any 
district of England entirely free from Anopheles, which 
areeasy to find if diligent search be made. 
He further states, on the authority of Dr. Daniells, that 
in the greater part of India blackwater fever is unknown ; 
on the contrary, however, this disease is more prevalent 
in some parts of India than in Africa. 
In that greater portion of the work which deals with 
the classification and descriptions of the mosquitoes, the 
author has prepared extremely serviceable and minutely 
detailed entomological accounts of the characteristics of 
all the then known species. Of the old genera, the fol- 
lowing have been retained :—Culex, Anopheles, des, 
Mochlonyx, Megarhinus, Psorophora, Sabethes, Core- 
thra, Uranoteenia, Heemagogus and Tzeniorhynchus 
(modified). The new genera added by Mr. Theobald 
are Wyeomyia, Deinocerites, 42deomyia, Panoplites, 
Eretmapodites, Janthinosoma, Stegomyia, Mucidus, 
Toxorhynchites and Trichoprosopon. 
Of the 300 species described, 136 are new. The 
majority of species described are those found in and 
around towns orare known pests to travellers and traders; 
a few, of the genera Megarhinus and Sabethes, which 
probably occur more abundantly in forests, are also 
described. 
The author deserves very great credit for the enormous 
amount of work which must have been entailed in the 
preparation of the details of this large number of species, 
and it is extremely desirable ‘that in its second edition 
the great value of the work, especially to those who are 
engaged in the study of disease in tropical and sub- 
tropical countries, will be still further increased by the 
correction of the errors and contradictions which have 
evidently been overlooked in the hurry of publication. 
THE DIRECT-CURRENT ARC. 
The Electric Arc. By Hertha Ayrton, M.I.E.E. Pp. 
xxv + 479. (London: The Zvectrician Printing and 
Publishing Company, Ltd.) Price 12s. 6d. 
HERE are few electrical phenomena which are of 
more interest than those exhibited by the electric 
arc, or which are more difficult to investigate. The 
complexity of the laws by which it is governed and the 
number of factors which can be varied independently 
make any research into its properties of a laborious 
character. Mrs. Ayrton is to be congratulated, not only 
on the painstaking investigations which she has carried 
out on the direct-current arc, but also on the remarkable 
success which has attended her work. Much of the book 
before us is already familiar as the result of papers 
