714 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the interior of the egg and form the endoderm. The larvae differed in 
some points from those described by Ganin. These larvae do not 
essentially differ from those of other orders. 
Pupal Stage of Culex.* — Dr. C. H. Hurst gives a description of the 
pupal stage of the Gnat. The pupa does not eat ; it floats, throat 
upwards, by virtue of a large air-cavity which lies under the hinder 
part of the thorax and the anterior part of the abdomen; in the 
abdominal part of the cavity there is, on either side, a large stigma 
which is held open by a fairly well developed cuticular lining and 
guarded by numerous spines. The cavity and stigmata are mainly, if 
not exclusively, hydrostatic in function, and serve not only to make the 
pupa float when at rest, but to make it float in a definite position with 
the thorax upward and the apertures of the respiratory siphons at the 
surface of the water. The pupae seem to be affected not by noise, but 
by tremors of the water, and the organs by which these movements are 
felt are probably the setae on the first segment of the abdomen. 
A detailed account is given of the external characters of the pupa. 
The alimentary canal has no convolution, except in the region of the 
intestine. At first the general structure is that of the larva, but during 
the pupal period great changes occur. The most striking is the reduction 
in thickness of the epithelium, which is best seen in the stomach ; changes 
of form occur in various parts of the alimentary canal. 
Three layers were recognized in the wall of the heart — an endo- 
cardium, which is an exceedingly thin layer of flat cells, with con- 
spicuous nuclei ; a middle layer which consists of encircling fibres, 
probably muscular ; and an outer fibrous layer, the fibres of which are 
mostly longitudinal in direction. The author denies the existence of 
the tracheal gills of Palmen. 
The nervous system is remarkable for the fact that, in the space of 
four days, certain ganglia increase enormously in size by the addition 
of cells, apparently derived directly from the epidermis ; while other 
ganglia, already well developed and functional, shift bodily from their 
original positions, and in some cases fuse with ganglia originally remote 
from them. A careful account is given of the formation of the large 
hemispherical basal joint of the antenna of the imago. 
The prostatic glands, though apparently simple, are seen in section 
to be double, though the cavities communicate posteriorly before opening 
into the common pouch ; this last is a dilatation of the ejaculatory duct 
at the base of the copulatory organ. The median oviduct is formed by 
invagination in what seems to be the ninth sternum, and as the anus 
opens lower down, there is no common cloaca. The author promises to 
work out in detail the development of the eye. 
Hermaphrodite Rudiment of Gonads in Male of Phyllodromia 
(Blatta) germanica.t — Herr R. Heymons gives an account of some 
points in the history of the formation of the genital organs in the male 
of this insect. They first appear at a very early stage in development, 
for genital cells are to be seen in the germ-stripes which show the 
* Studies Biol. Lab. Owens Coll., ii. (1890) pp. 47-71 (1 pi.), 
f Zool. Anzeig., xiii. (1890) pp. 451-7. 
