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DESCRIPTION OF FILA1UA MAVIS, n. sp., FKOM 



THE THRUSH. 



By Robert T. Leiper, M.B., F.Z.S., 



Helininthologist to the London School of Tropical Medicine. 



The blood of birds, both in this country and in the Tropics, 

 often swarms with minute larval nematodes. The parental 

 forms that give rise to these young are seldom obtained without 

 a very detailed examination of all the tissues of the host. Thus 

 it happens that while the characters of the embryo are frequently 

 quite well known, those of the adults escape investigation. 



Several observers have reported a high percentage of Black- 

 birds and Thrushes in Great Britain to be heavily infected with 

 microfilaria, but none describe systematically the mature worms. 



A short time ago I examined a couple of Thrushes in Inver- 

 ness-shire ; both showed numerous sheathless microfilariae in the 

 blood. The adults were discovered, in a bursa in close associa- 

 tion with the ankle-joint, when the skin of the leg was reflected 

 over the metatarsus. The only other round worm found in these 

 birds was a solitary Spiroptera turdi in the walls of the stomach. 

 There were several filaria in each bursa. They had the appear- 

 ance of short lengths of softened catgut, and were of two sizes, 

 the males being only half as long as the female w T orms. 



Description of the Male Worm. 



Total length 6 mm., greatest diameter 0*2 mm. This thick- 

 ness is maintained uniformly over the middle 2 mm. of the 

 body ; from that region the worm tapers anteriorly to 0*16 mm. 

 at the commencement of the chyle intestine, and abruptly to 

 0'05 mm. at the level of the nerve-ring within 0*1 mm. of the 

 anterior end of the body. Posteriorly also the worm tapers 

 gradually to 0'16 mm. at 1 mm. from the tip of the tail, which 

 is bluntly pointed, the last 1 mm. being coiled to resemble a 

 "note of interrogation." The skin is smooth and without 

 spines in any region. The mouth is simple, there is no oral 



Zaol. 4th ser. vol. XIIL< September, 1009. 2 i> 



