ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 347 



Observations on Pinna.* — Mario Stenta gives an interesting account 

 of the structure of Pinna, in which he seeks to correlate the peculiarities 

 of structure with the peculiar nature of its sedentary life, which is quite 

 different from that of mussel, oyster, Pholas, or any other sedentary 

 bivalve. 



Movements of Cyclas.f — F. Martin describes how small specimens 

 of Cyclas or Sphserium glide along beneath the surface film exuding a 

 double trail of mucus. From the pallial slit drops of mucus are passed 

 out at regular intervals, corresponding to the expansion and contraction 

 of the foot, but more rapidly. 



Arthropoda. 

 a. Insecta. 



Treatise on Entomology. :£ — A. Berlese deserves congratulation on 

 the completion of the first volume of his great work on Insects. The last 

 instalment deals with the reproductive organs, oogenesis, spermatogenesis, 

 and related topics. 



Sense of Direction in Bees.§ — Gaston Bonnier has studied the return 

 of bees, from a distance of up to three kilometres, straight to the hive. 

 Bees carried afield in a box find their way to a hive hidden behind woods. 

 Bees blinded with blackened collodion find their way. Therefore vision 

 is not necessary. The removal of the antennae, wilich bear the so-called 

 olfactory organs, does not prevent the return. Experiments show that 

 bees are capable of distinguishing between two directions which form a 

 very acute angle. Everything points to the conclusion that bees have 

 a particular " sense of direction," more or less comparable to that of 

 carrier pigeons, which has its seat in the cerebral ganglia. 



Metamorphosis in Isosoma graminicola.|| — W. Docters van Leeuwen 

 has studied in particular the changes in the structure of the food-canal 

 in this gall-making Chalcid. We select the part dealing with the mid- 

 gut. In the young larva the intestinal wall consists of a layer of intes- 

 tinal cells and muscle-cells ; during the growth of the larva wandering 

 cells insinuate themselves between the muscularis and the larval epithe- 

 lium, and become imaginal intestinal cells. When nutritive material 

 begins to be taken from the galls the imaginal cells show a vacuole 

 which gradually increases in size. The larval cells increase and so do 

 the imaginal cells. The latter approach one another and form a new 

 intestinal epithelium. In the beginning of the pupal life the larval cells 

 are destroyed, and the imaginal cells lose their vacuoles. By a shortening 

 of the mid-gut the imaginal cells are pressed together and acquire their 

 definite form. The muscle-cells disappear and are replaced from wan- 

 dering cells. 



The author deals also with the fore-gut and the hind-gut. He 



* Atti R. 1st. Veneto. lxvii. (1908) pp. 495-518. 



t SB. Ges. Nat. Freunde Berlin, 1908, Nos. 2 and 3, pp. 38-40 (3 figs.). 



j Gli Insetti. Milano, 1909, pp. i-xii, 897-1004 (3 pis., and figs. 1198-1292). 



§ Comptes Rendus, cxlviii. (1909) pp. 1019-23. 



|| Tijdscbr Nederland. Dierk. Ver., xi. (1908) pp. 1-35 (2 pis.). 



