604 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Arthropoda. 

 a. Insecta. 



Joints of the Walking Legs in Insects and Myriopods.* — Carl 

 Bonier discusses the difficult question of the homologies of the various 

 joints of the walking appendages in Myriopods and Insects, — the coxa, 

 the trochantero-femur, the tibio-tarsus, and the praetarsus — working 

 from the simplest cases in larvae of Thysanoptera on to the more 

 specialised forms. 



Metamorphosis of Nervous System in Insects.j — V. Bauer has 



studied representatives of seven orders, and finds that the central 

 nervous system has by no means attained its definitive structure when 

 the larva or young form is hatched. There is a new formation of 

 ganglia (both sensory and motor centres) and of their protective tissue 

 and tracheae. 



Until the beginning of the metamorphosis the ganglia show aggre- 

 gates of neuroblasts which produce by unequal division a series of 

 mother-ganglion-cells. These divide equally to form ganglion-cells. 

 Finally the proliferating power of the neuroblasts ceases and they 

 degenerate. The same process occurs in ametabolic insects, but more 

 continuously. 



The enveloping tissue of the imaginaJ ganglia is due to the immigra- 

 tion of connective-tissue cells from the cavity of the body. Tracheae 

 enter from particular points in the peritoneum where there is active 

 proliferation. The connective tissue and trachese of the larval ganglia 

 are absorbed by phagocytes, but these do not seem operative in the dis- 

 solution of the ganglion-cells. 



Insects and Petal-less Flowers.J — G. W. Bulman directs attention 

 to Plateau's experiments § on poppies (Papaver orientate) which were arti- 

 ficially deprived of their petals, the number of insects visiting the 

 remaining parts being carefully noted and compared with the number 

 of those visiting neighbouring intact flowers. Plateau contends that 

 the insect-visitors are not attracted by the brilliant colours of the 

 blossoms, but rather by the perception in some other way — probably by 

 scent — that there is honey or pollen to be had. Great care was taken 

 in the experiments to avoid touching any of the remaining parts of the 

 flower with the fingers, for Plateau believes that insects have a keen 

 sense of smell and dislike the scent of human fingers. On taking an 

 average, it was found that each of 30 petal -less flowers received 4*5 

 visits, while each of 70 intact flowers received 2*4 visits. Bulman has 

 seen bees visiting flowers of Geranium phaaum, rockrose, bramble, and 

 sage which had lost their petals. 



Insects and Flowers. || — E. Ernest Lowe in referring to Plateau's 

 experiments on poppies, &c, artificially deprived of their petals, argues 



* SB. Ges. Naturfr. Berlin, 1902, pp. 205-29 (2 pis.). 



t Zool. Anzeig., xxvi. (1903) pp. 655-6 (2 figs.). 



J Nature, lxvii. (1903) p. 319. 



§ Bull. Acad. Roy. Belgique, November 1902. 



|| Nature, lxvii. (1903) pp. 368-9. 



