48 SUMMA.KY OF CUKRENT KESEARCHES RELATING TO 



Tropisms of Earthworm. — L. H. Bittner, G. R. Johnson, H. B. 

 ToRREY {Jouni. Animal Behavioi/r, 1915, 5, Gl-5). Tropism hypotheses 

 agree iu exdudino; the conception of orientation by trial reactions. 

 Fnndamental to all of them is the conception of orientation by means of 

 movements that, with reference to a given source of stimulation, are 

 predictable as to direction. The conception of the " method of trial " 

 has been used to supplement tropism theories. Experiments with earth- 

 worms have shown that photic stimulation, far from inducing random 

 movements, immediately calls forth reactions in a definitely predictable 

 direction. Like the sow-bug (ForceUio) the earthworm must be placed 

 in that group of organisms whose orientation to light is determined 

 essentially by movements that are predictable as to direction, and hence 

 neither random movements nor " trials." J. A. T. 



Nematohelminthes. 



Nematodes of Clean Earth. — J. G. de Man {Tijdschr. Nederland. 

 Dierk. Ver., 1917, 16, 103-19). An account of a collection of fifteen 

 species from clean earth at Atna in Norway. The total list of Nematodes 

 from similar habitats in Norway is now twenty-eight ; the new collection 

 includes DoryJaimus consolrinus sp. n. J. A. T. 



Free-living Nematodes from Mountain Lakes of Peru. — 

 G. Steiner {Revue Suisse ZooL, 1920, 28, 11-44, 22 figs.). From 

 lakes Huaron and Naticocha, at a height of 5140 metres above sea-level, 

 a collection of free-living N.ematodes was made, including Flectas 

 naticochensis sp. n., Mo7iohysUra {Afonohi/streUa) godeti^^. n., Aphelmchus 

 naticochensis sp. n., Dorylaimus incae sp. n., and eleven other forms, all 

 of which are described. J. A. T. 



Habronema in Horses. — Lionel B. Bull {Trans. Proc. R. Soc. 

 S. Australia, 1919, 43, 85-141, 3 pis.). A granulomatous condition 

 found most frequently affecting the external mucous membranee of the 

 horse in Southern Australia is due to the presence of the larval stages of 

 three species of Habronema, a genus of Nematodes. The tissue reaction 

 following the introduction of the larva gives rise to a characteristic 

 tumour. The larvie are only to be found in lesions up to three weeks' 

 duration. Evidence suggests that they are deposited on moist surfaces 

 by Musca domestica, which acts as the intermediate host of H. mnscse 

 and H. megastoma. When deposited on the external mucous membranes 

 the larvte appear to be capable of pushing their way through the 

 membrane and of entering the submiicosa. On other parts the larvas 

 suffer desiccation unless there is some exudation of blood or serum, sncli 

 as may be produced by biting flies like Stouioxys calritrans. It appears 

 that H. megastoma is chiefly responsible for the infection. '" Swiimp 

 cancer " is a similar granuloma which may be due to H. microstoma 

 possibly introduced by Stomoxgs. It may be that much the same is true 

 in regard to "Leeches" in North America and " Bursattee " in India. 

 The adult Nematodes occur in the stomach, and it is important lo get 

 them expelled and to get rid of loo.^e liorse-dung. J. A. T. 



