170 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
observations of Weismann on the development of the compound eye. 
Prof. Lowne comes to the conclusion that the retina is entirely 
formed as an outgrowth from the central nervous system, while the 
diojitron is formed from the external epiblast which is more or less 
invaded by mesoblastic elements. 
Structure and Development of Ovaries of Blowfly.* — Prof. B. T. 
Lowne states that the “ ovarian eggs ” in the blowfly, and probably in 
other Insects, are yolks and contain no germ, while the so-called germ- 
glands are really germ-glands in which the germ-ova are developed. 
These ova pass into the yolks during their passage through the oviducts 
either as naked germinal vesicles, or as female pronuclei. The author 
urges the evidence of the observations made by himself, and the state- 
ments of other authors, when examined critically, as supports for the 
startling conclusions at which he arrives. 
Habits and Metamorphoses of Eucephalous Larvae of Diptera.f — 
Mr. F. Meinert has made a study of Gulex, Anopheles, Corethra, 
Mochlonyx, Chironomus, Tanypus, Dixa, Simidium, and Ceratopogon. 
He finds that the epicranium varies in size and extent ; for it may 
occupy the whole of the superior region of the head as in Corethra, or 
only a third or a fourth as in Dixa and Simulium. The eyes may be 
large and compound as in Gulex or very small and simple as in Chiro- 
nomus and others. Though the ocelli are small they are sometimes 
larger than the true eyes. As a rule, the antennee are large, but in 
Ceratopogon they can be only just detected. The scutum of the third 
metamere is ordinarily well developed, though here, again, there are 
exceptions ; that of the second metamere is rarely very distinct. The 
sides of this metamere often carry a tuft of setae or plates (rotatory 
organ) which attains the highest development in Simulium, although of 
large size in Gulex, Anopheles, and Dixa. The first metamere (as 
opposed to the mouth) is always poorly developed or even rudimentary, 
and especially is this the case with the labrum. The labium is always 
devoid of palps, and has often the form of a strongly cornified layer, the 
anterior edge of which is denticulated. The maxillae generally have 
only one large lobe ; it is rare^ that there are two which are distinct. 
The palps are always distinct, except in Ceratopogon, where the maxilla3 
are altogether rudimentary. The mandibles may be simple, and have 
few or many rows of setae, together with a large multifid tooth or a fan 
of dorsal plates. 
The segments of the thorax are sometimes free and distinct ; some- 
times the anterior segment is alone free, and sometimes all three are 
almost fused. The nine segments of the abdomen are quite distinct ; 
the eighth often carries two stigmata, either directly on the back or at 
the end of a rather long tube — the respiratory tube. In a larger 
number of cases the stigmata are completely wanting. Some species of 
Chironomus may push out two long tubular protuberances from the 
eighth segment. The ninth segment often carries a natatory fan. As 
a rule there are four anal papillae, and a more or less large number of 
anal setae at the extremity of this segment. Corethra and Mochlonyx 
* Joimi. Liiin. Soc., xx. (1889) pp, 418-41 (1 pL). 
t Skrift. K. Dtiuske Vid. Selsk., iv. (1880) pp. 373-493 (4 ids.). 
