34 Ensheathed Larvae of sortie Parasitic Nematodes 



The adult females of all three species produce eggs which pass out 



in the faeces of the host. 



MATERIAL. 



Through the kindness of Dr C. F. Druitt of Alvaston, Derby, I was 

 able to obtain a supply of material for this research. Dr Druitt has the 

 shooting rights of some fields where the rabbits were noticed to be 

 suffering from certain wasting conditions towards the end of 1920. One 

 or two specimens of these diseased rabbits were sent to this department 

 and were found to contain large numbers of the two parasites in question. 



In the early part of this year, 1921, I got into touch with Dr Druitt 

 and he very kindly supplied me with rabbit droppings from the same 

 areas where the wasted rabbits had occurred. At another time he sent 

 three live rabbits, two of which turned out to be heavily infected with 

 G. strigosum and T. retortaeformis, and furnished a good supply of 

 droppings containing eggs, until they died after being in captivity for 

 a short time. On opening these rabbits large numbers of both parasites 

 were found. 



I should like to express my best thanks to Dr Druitt for the interest 

 he has taken in the work and for the great assistance he has given in 

 providing material. 



The larvae of N. americanus were obtained in cultures from the faeces 

 of one of the patients in the Hospital for Tropical Diseases. 



CULTIVATION OF THE LARVAE. 



By teasing out a few droppings from an infected rabbit in water it 

 was easy to find the eggs of both G. strigosum and T. retortaeformis. In 

 the case of mixed collections of droppings from the infected area, which 

 have been used in this work, it was possible to recognise the eggs of 

 both worms. Identification was an easy matter also, in that a good 

 supply of adult worms was available, and these furnished the necessary 

 eggs for comparison and measurement. 



A number of rabbit droppings were broken down in distilled water 

 until a fairly thin mixture was obtained. This was put into a Petri dish 

 in a shallow layer. The lid of the dish was provided with a layer of clean 

 blotting-paper which was kept moist, and afterwards the dish was put 

 into the incubator at 22° C. 



Numerous rhabditiform larvae developed in this culture, but became 

 quiescent on the bottom of the dish after about two days and failed to 

 develop further. This was probably due to the presence of toxic sub- 

 stances in the culture, so recourse was had to Looss's recommendation 



