722 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nematohelminth.es. 



New Species of Pseudalius.* — 0. von Linstow describes Pseudalius 

 ovatas sp.n. from the gullet and stomach of a dolphin (Delphinus tursio), 

 and makes a note on the characters of the genus, which belongs to 

 Schneider's Holomyaria, and, according to the longitudinal areas, to the 

 Resorbentes. The eight other species have been found in the respiratory 

 tract, heart and blood-vessels of marine Mammals, so that the new species 

 is an exception in this respect. 



Filaria in Turkey's Eye.f— M. Ozoux reports the frequent occurrence 

 of Filaria? below the nictitating membrane in the turkeys of Reunion. 

 As many as eight may occur in one eye. They soon die when removed 

 into artificial media. There are none in the blood. The author refers 

 the parasites to Oxyspirura mansoni,a, species which occurs in the eye of 

 the fowl. 



Significance of Chitin in Nematode Development.! — Jammes and 

 Martin point out that the chitinous envelope of the egg is resistant to 

 digestive juices and many chemical reagents, and that it assists survival 

 in manifold conditions. In homoiothermal hosts, the parasitism is 

 furthered by the physico-chemical properties of the chitin. If the tem- 

 perature is low, the shell retains a relative impermeability ; when the 

 temperature rises, the permeability increases. " The chitin is a barrier, 

 never quite shut, between the egg and the milieu. It opens more and 

 more as the temperature rises, which corresponds, in natural conditions, 

 to meeting the definitive host." 



*& 



Hermaphroditism among Free-living Nematodes. § — F. A. Potts 

 publishes an account of his study of the hermaphrodite species of free- 

 living Nematodes, especially the two forms Rliabditis gurneyi and Diplo- 

 gaster linstowi. His investigation confirms the work of Maupas, and 

 adds some further details. In one hermaphrodite species, Diplogaster 

 maupasi, the residual males are much more numerous than in any other 

 yet studied, and in small cultures they may reach 30 p.c. of the whole 

 number of individuals. The secondary male sexual characters, i.e. bursal 

 papillae and accessory copulatory spicule, show great variability. The 

 production of males is cyclical ; periods (each lasting a few generations) 

 when males are frequent alternate with others in which only herma- 

 phrodites are produced. Attempts to affect the sex-ratio artificially 

 proved unsuccessful. It was also found impossible to increase the pro- 

 portion of males by selection from favourable cultures. No rule could 

 be discovered governing the constant fluctuations of production. Even 

 when males were most common, there was no tendency to find females 

 or partially hermaphrodite individuals, and the males were sexually 

 inactive. The number of fertile eggs laid by D. maupasi is subject to 

 wide variation. In Rhabditis gurneyi a far greater number of fertile 

 eggs may be produced by a single individual than in any other herma- 



• 



Centralbl. Bakt. Parasitenk., lv. (1910) pp. 133-5 (3 figs.). 

 + C.R. Soc. Biol. Paris, lxviii. (1910) pp. 974-5. 

 % Gomptes Rendus, cli. (1910) pp. 250-1. 

 § Quart. Journ. Micr. Sci., lv. (1910) pp. 423-84 (11 figs.). 



