198 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Blow-fly Larvae and Gravity.*— S. 0. Mast has investigated the 

 statement of Loeb that blow-fly larvae "swim downward " in water, but 

 has found that they do not react to gravity, either in water or out of it. 

 " In air they may be found to orient and crawl nearly straight upward 

 on objects, but this is not due to a response to gravity on the part of the 

 organisms. In water they sink to the bottom or float at the top, depend- 

 ing upon the amount of gas they contain, but there is no evidence 

 whatever indicating that they can swim." 



Metamorphosis of Blow-fly. f — C. Perez has done a very fine piece 

 of work in his histological account of the metamorphosis of Calliphora 

 erythrocephala. He refuses to subdivide the nymphal period into two 

 successive phases of histolysis and histogenesis, for what occurs is a pro- 

 gressive substitution, and the beginning of histogenesis actually precedes 

 that of histolysis. The parts that disappear entirely are the parts most 

 specialized for larval life ; the parts that are built wholly de novo from 

 embryonic histoblasts are the parts most specialized for adult life. The 

 less specialized parts, which are more plastic, are re-organized in situ. 

 The importance of phagocytosis, recently doubted by some critics, is 

 made doubly clear by the author's careful work. 



Oviparity and Viviparity in Dung-fly. J — E. Roubaud finds that 

 Musca corvina Fab. in tropical Africa is viviparous all the year round, 

 and may produce a larva every four days. This viviparity requires for 

 its manifestation an average temperature of at least 30° C. The con- 

 stant viviparity is interesting, for Portchinsky has shown that in the 

 north of Russia 31. corvina is constantly oviparous, laying regularly 

 2i eggs, while in the Crimea it gives birth to a large larva at the end of 

 spring and in summer. 



Suctorial Disks of Male Dytiscids.§ — Oskar Torne gives a careful 

 account of the structure and mode of action of these familiar organs. 

 The unicellular glands, which Graber interpreted as producing an adhesive 

 secretion, open not on the sucker itself, but in a circle at the base of the 

 stalk. They have nothing to do with adhesion, but may produce a sort 

 of varnish for the setae, so that the air between the setae is less readily 

 displaced by the water. The adhesion is mechanical ; the suckers of 

 preserved specimens work effectively. 



Oogenesis in Dytiscidae.|| — Thomas Giinthert has studied the ovary 

 of Dytiscus and Colymbetes, and describes the origin of the ova and 

 nutritive-cells, the relations between them, and the secretory function of 

 the nutritive-cells. 



Respiration in Donacia and Macroplea.lf — Johannes Deibel has 

 studied the habits of these water-beetles, with especial reference to their 

 respiration. The larvae live on the roots and rhizomes and between the 



* Biol. Bulletin, xviii. (1910) pp. 191-2. 

 t Arch. Zool. Exper., iv. (1910) pp. 1-274 (16 pis.). 

 % Comptes Rendus, clii. (1911) pp. 156-8. 

 § Zool. Jahrb., xxix. (1910) pp. 415-48 (2 pis.). 

 || Op. cit., xxx. (1910) pp. 301-72 (7 pis. and 2 figs.). 

 1 Op. cit., xxxi. (1910) pp. 107-60 (2 pis. and 3 figs.). 



