608 SUMMARY OF CUEEENT RESEARCHES RELATING TO 



Arthropoda. 

 a. Insecta. 



Metamorphosis of Malpig^hian Tubes.* — A. Hufnagel has studied 

 this in Eijiionomenta padeJIa, and finds that what occurs during meta- 

 morphosis is much the same as in the case of the silk-glands. Part of 

 the apparatus entirely disappears. Another part persists, loses the basal 

 membrane, and differentiates into an imaginai organ. 



Tracheal Vesicles in Musculature.f — Ivar Thulin discusses the 

 peculiar interstitial vesicles which occur in connexion with tracheal 

 branches among the muscle-fibres. He describes in particular, in Ilybius 

 ater, a water-beetle, the occurrence of numerous vacuoles among the 

 muscle-fibres. The intra-muscular tracheal branches consist of a homo- 

 geneous chitinous tube, a cellular layer, and a basal membrane. In 

 the formation of the large vacuole-like structures, the cellular layer is 

 reduced, the chitinous tube is enlarged and becomes much thinner, until 

 only a delicate membrane is left. These vacuoles represent a special 

 modification of the tracheal branches. They contain a serous fluid and 

 have an ancillary respiratory function. 



Chromosomes in Species of Stenobothrus.J — C. F. U. Meek has 

 studied the spermatogenesis of this Acridiid with special reference to 

 his theory of a correlation between somatic characters and chromatin 

 rod-lengths. Each ordinary spermatogonial and secondary spermatocyte 

 chromosome of Stenohothrus curiipennis is composed of two equal rods, 

 and each primary chromosome of four. The diameter of these rods is 

 invariably 0'8?> fi, and consequently lends further support to the 

 assumption that the chromatin thread-width is constant in all organisms 

 above and including Nematohelminthes. 



The lengths of the ordinary rods constitute members of a general 

 series in arithmetical progression ; the fine short chromosomes are 

 identical with those of other members of the genus, but the lengths 

 of the three long chromosomes once more enable the species to l)e 

 identified. 



A comparison between S. parallelus, S. irridulus, S. Mcolor, and 

 S. curtipennis fails to establish correlation of somatic characters and 

 chromosome rod-lengths. But the author thinks that the obvious 

 characteristics upon which identification of species is based are in some 

 way connected with the three long chromosomes. Present failure is 

 probably due to ignorance of the less obvious somatic characteristics, 

 and to the lack of trustworthy methods of identifying corresponding 

 chromosomes in the respective complexes. 



Sting of Ants.§ — Emil Foerster has made a comparative study of 

 the stinging apparatus in ants. It shows considerable diversity in its 



♦ C.R. Soc. Biol. Paris, Ixxii. (1912) pp. 100-2 (4 figs.), 

 t Anat. Anzeig., xli. (1912) pp. 465-77 (10 figs.), 

 t Linn. Soc. Journ. ZooL, xxxii. (1912) pp. 107-19 (5 figs.). 

 § Zool. Jahrb., xxxiv. (1912) pp. 347-80 (2 pis. and 3 figs.). 



