ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 197 



to the neurites. The muscle-fibres are innervated in two ways. Either 

 the plasma of the muscle-cell is in direct connexion with the cells of 

 the plexus, or the whole muscle-fibre is surrounded by a network of 

 nerve-fibres. These are but a few of the many points in this paper. 



Arthropoda. 

 «• Insecta. 



Insects of the Rhine.* — Ferdinand Neeracher has made an interest- 

 ing study of the larval and adult insects found in the Rhine and its 

 tributaries, with especial reference to the seasonal changes and the life- 

 histories. He discusses the mouth-parts of Perlidas, some new or 

 unknown species of Perlidas and Eohemeridae, and the male dimorphism 

 in Perla cephalotes Curt., and Dictyopteryx microcephala Pict. 



Studies on Bees. — Enoch Zander f gives an analysis of the thoracic 

 skeleton in the hive-bee and in wasps, and sketches the development 

 from the larva onwards. The much-discussed waist is an extremely 

 developed intersegmental groove, between the fourth and fifth segment. 

 The fourth ring is displaced on to the dorsal wall of the thorax, while 

 the fifth segment becomes the stalk and the front wall of the abdomen. 



F. StellwaagJ describes the movements of the wings in flight, the 

 mechanism involved, and the musculature. All the parts are so wonder- 

 fully connected that a single muscular pull suffices to set all the move- 

 ments going. It has only a single point of insertion at the root of the 

 wing. 



Junction of Fore-gut and Mid-gut in Hive-bee.§— Christian Metzer 

 finds that all the parts of the abdominal connecting portion between 

 fore-gut and mid-gut are differentiations of the fore-gut, which ends 

 blindly. These differentiations are established, in the earliest pupal 

 stages, far forward in the thorax, as a row of successive chambers. They 

 are secondarily displaced into the abdomen. The funnel, which regulates 

 the passage of food into the mid-gut and prevents regurgitation into the 

 honey-sac, is homologous with the gizzard in other insects. 



Species and Varieties of Humble-bees. || — H. Friese and F. von 

 Wagner have made a very careful and interesting study of the German 

 species of Bombus, discussing the extraordinary variability (with 

 parallelism, convergence, and other phenomena), and their phyletic 

 relations to one another. Tables are given contrasting Bombus with 

 other bees, contrasting queen and drone Bombus with the queen and 

 drone of its Doppelgdnger Psithyrus, contrasting the queens of the 

 fifteen German species, showing the times of appearance, and the size. 

 Finally the main varieties of the fifteen species are dealt with in an 

 elaborate table. 



* Rev. Suisse Zool., xviii. (1910) pp. 497-590 (19 figs.). 



t Zeitschr. wiss. Zool., xcv. (1910) pp. 507-17 (1 pi. and 8 figs.). 



t Tom. cit., pp. 518-50 (2 pis. and 6 figs.). 



§ Op. cit., xciv. (1909) pp. 539-71 (2 pis. and 2 figs.). 



|| Zool. Jahrb., xxix. (1910) pp. 1-104 (7 pis. and 20 figs.). 



