468 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Arthropoda. 
«• Insecta. 
Histolysis and Histogenesis of Muscular Tissue in the Meta- 
morphosis of Insects.* — Prof. A. Korotneff, bearing in mind tho work 
of preceding investigators, asks the following questions. As the definite 
muscle-nuclei are directly descended from the nuclei of the larval 
muscles, what is the definite part played by the mesenchyme-cells and 
their nuclei in the formation of the muscles of the imago ? Where do 
the muscle-fibres arise, and in what way ? The plasmatic cords which, 
according to Van Rees, must take part therein, are very doubtful and 
quite special structures. How do the other muscles of the body arise ? 
If as Kowalevsky states, then the plasmatic cords are quite unnecessary 
structures, and the development of the other muscles of the imago is solely 
due to the mesenchyme-cells. But this double origin of muscles in one 
form seems scarcely probable. 
The author’s own observations have been confined to Tinea , where he 
finds that the following are the chief points in the metamorphosis. 
There are no special mesenchyme-cells in the larva ; the coelom contains 
only leucocytes and granule-spheres. The leucocytes take absolutely no 
part in the degeneration of the tissues. The formation of all the 
imaginal muscles is to be regarded as a re-formation of the larval 
muscles. In the thorax some muscles disappear, and only the three 
pairs mentioned by Van Rees are transformed into the definite thoracic 
musculature of the Moth. 
The resorption of the muscles is effected in the following way ; the 
fibrillar portion becomes granular and draws itself together ; the nuclei 
multiply chiefly on one side of the muscle. 
The altered muscle consists at last of a fibrous and a granular part 
which run parallel to one another, at the same time the primitive bundle 
is resorbed, and without the leucocytes taking any part in it. The 
nuclear cord soon separates from the muscle, and begins to move off 
from the surface ; it soon produces new fibrils, which, at first, are hardly 
to be distinguished ; later on, the fibrils have the form of rhomboidal 
structures, which are imbedded in the plasma of the nuclear cord 
between the nuclei. In a longitudinal section the earlier, atrophied, and 
the newly developed muscles form two parallel bands, and possess two 
distinct tendons. In an advanced pupa of Tinea , no signs of the larval 
muscles are to be detected, for after becoming gradually smaller, they 
have finally been resorbed. Instead of them there are to be seen, in 
transverse sections, well-marked spots which stain deeply with haemato- 
xylin, and are an expression of the nuclear cords in which the muscle- 
fibrils were laid down. In the further development of the definite 
muscles the muscle-fibrils collect into bundles, which, in cross-section, 
are seen to be fringed with muscle-nuclei. 
This mode of metamorphosis of muscle appears, from a theoretical 
standpoint, to be logical and quite intelligible ; and the author’s obser- 
vations are quite in keeping with the pathological phenomena sometimes 
seen in the muscles of higher animals. 
Lower Senses of Insects.f — Dr. W. Nagel points out that the dermal 
sensory organs of Insects, which are hairs, cones, and porous plates or 
* Biol. Centralbl., xii. (1892) pp. 261-5 (5 figs.). 
f ‘ Die niederen Sinne der Insekten,’ Tubingen, 1892, 8vo, 68 pp., 1 pi. 
