ZOOLOGY AND BOTANY, MICKOSGOPY, ETC. 7o 



}>fninsula of India ; and 0. f/ibsoni in B. indicus in the Malay peninsula, 

 and us a very variable form in B. taurus in Australia and most probably 

 the Malay Archipelago. The oiigiiial parasite and its original host 

 are probably to be songht for in the Indo-Malayan gaur {B. gaurvs) or 

 wild ox. (ir its closely allied species the ban tin {B. hanteng), from which 

 also 0. (jutttirosa may be derived indirectly through 0. indica. 



Life-history of Nematodirus filicollis.* — C. L. Boulenger has 

 studied the life-history of this common parasite of the duodenum of 

 sheep, especially of lambs and yearlings. The eggs when laid contain 

 an embryo with seven or eight cells. They pass out of the host with 

 the faeces. Even under favourable conditions development takes place 

 sloAvly, and the embryos are not ready to hatch until twenty-four to 

 twenty-eight days have elapsed. In their early stages the embryos are 

 not able to withstand desiccation and are killed if frozen or subjected to 

 high temperatures. 



While still within the egg-shell the embryo undergoes two ecdyses, 

 and when ready to hatch is enclosed in a tightly fitting sheath formed 

 by the incompletely cast skin of the second moult. The larva3 on libera- 

 tion from the egg-shell are therefore in a more advanced condition than 

 those of most other Strongyiids (e.g. Hxmonchus or Anchylo stoma), and 

 are in a stage comparable to that reached by the latter at the end of 

 their period of free existence. The sheathed larvit; are often retained 

 for a long time within the egg-shells, and both in this position and after 

 hatching can resist complete desiccation for considerable periods, twenty 

 months or even longer. When dried they are able to withstand freezing 

 as well ;i.s temperatures much above those likely to be met with in the 

 open. 



The free larva? will live for a considerable time in water ; they possess 

 well-developed migratory instincts and climb vertical surfaces, such as 

 grass stems and blades, and the glass walls of vessels in which they are 

 kept. The sheaths are cast off by the larvae when these are subjected 

 to temperatures approximating to the blood-temperature of the host ; 

 completion of the second moult occasionally also occurs at laboratory 

 temperatures under certain abnormal conditions. No infection experi- 

 ments were made on sheep, but other evidence shows that these animals 

 are infected by swallowing the sheathed larvte, either when free or whilst 

 still enclosed in the egg-shells. A number of young stages of the para- 

 site were met with in the intestines of sheep, the smallest of these being 

 only a little more advanced in structure than the larvae just after ecdysis. 



Platyhelminthes. 



Avian Gestodes.f — Frank E. Beddard gives an account of the struc- 

 ture of Chapmaaia taarirolUs, from the right caicnm of a Rhea, de- 

 scribing in particular the genital organs. He discusses the members of 

 the sub-family Idiogeninfe, marked by the presence of a single paruterine 



* Parasitology, viii. (1915) pp. 133-54 (2 pis. and 5 figs.). 

 t Proc Zool. Soc, 1915, pp. 429-43 (6 figs.). 



