ZOOLOGY AXD HOTANY, MICROSCOPY, ETC. 49 



Hereditary Resistance to Heterodera schachtii. — H. Xilsson-Ehlk 

 (Hereilitas, 1920, 1, 1-34. 4 titjs.)- The first article in this new journal 

 of .2:enetics, published by the Meudelian Society of Lund, deals with 

 resistance to this eel-worm. In contrast to wdiat is true in other cereals 

 there are amont; barleys striking variations in resistance to Heterodera 

 schachtii, for which some kinds are susceptible, others quite immune. 

 Both states are heritable. The quality of immunity behaves as a 

 dominant unit character ; there is typical segregation in the second and 

 third filial generations. The quality of immunity, can be combined 

 with other qualities in the usual Meudelian fashion. Even infected 

 plants of barley are not greatly damaged, but it is very different with 

 oats and wheat. Therefore the cultivation of susceptible barleys is to 

 be avoided, since it implies fostering the Nematodes in the soil, and thus 

 lessening of the yield of oats and wheat afterwards sown in the same 

 ground. Several of the best barleys of South Sweden are susceptible. 

 It is pi'acticable by crossing to attach to the good qualities of these kinds 

 the quality of immunity, replacing that of susceptibility. Thus Itarleys 

 may be grown which will favour the yield in other cereals. J. 1. T. 



Important Nematode Parasite of Chickens. — James E. Ackert 

 (Proc. Amer. Soc. ZooL in Anat. Record, 1920, 17, ;531-2). A study of 

 the development of Ascaiidia perspiciUam, which matures in the small 

 intestine of chickens. The female may contain 1200 eggs. These 

 develop in the intestine, showing larvae in nine days. Eggs containing 

 larv» give rise to free motile larvte in twenty-eight hours or so if they 

 are ingested. After three days' sojourn in the chick's intestine the 

 larva? have doubled their length. J. A. T. 



Observations on Gordius. — G. W. MiJLLER {Zool. Anzeig., 1920, 

 51, 225-9). In small pools which dry up in summer large numbers of 

 Parachordodes tolosanus were found, sometimes seventy coiled together. 

 Most came from a Carabid beetle, Pterostichus niger ; some from 

 jVebria picicornis, also a Carabid. The larvie may survive the winter in 

 damp mud, and the same may be true of late-laid eggs. It does not 

 seem to be true of adults. Larva3 occur in larvte of Dytiscus w-hich are 

 probably infected directly.. Larvae (probably of Parachordodes) were 

 also found in an Enchyfcri\^id {Friihricia), and there were Gordins-laryse 

 in larvse of Limnobiida3 (Pedicia rivosa and Dicranota sp.), which may 

 feed on Fridericia. But no pupae or adults were found in the adult 

 Limnobiidfe. The author's general view is that the whole development 

 may take place simply without an intermediate host before the definitive 

 beetle-host is reached. J. A. T. 



Structure and Development of Gordius robusta. — H. G. May 

 {Proc. Amer. Soc. Zool. in Anat. Record, I'd 20, 17, 332-8). There is no 

 complicated metamorphosis in this parasite of Locustidae, but the larval 

 cuticle and the hooks of the proboscis are shed at the end of the 

 parasitic period. The adult cuticle is formed from differentiated parts 

 of the hypoderm cells ; the bristles are part of the fibrous cuticle. The 

 intestine is never open anteriorly. Muscles and parenchyma arise from 

 mesenchyme cells ; the parenchyme cells form a solid mass filling nearly 



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