154 NEMATHELMINTHES 



and may live in damp earth, moss, etc., for months without taking 

 nourishment, until the autumn, when they become sexually mature 

 and, according to Leuckart, pair. The fertilised female is believed 

 to bore her way into the humble-bee whilst the latter is seeking 

 her underground winter quarters ; this accounts for the fact that 

 only queen bees are infected. The parasite is widely distributed 

 both in Europe and North America ; it is found in many species 

 of Bombus, but most frequently in B. lapidarius and B. terrestris. 

 The presence of the Sphaerularia affects the reproductive organs 

 of the host, and reduces their fertility, so that an infected queen 

 bee never succeeds in forming a colony. 



VI. Family Anguillulidae. 



For the most part free living and of small size. The oeso- 

 phagus has usually a double swelling or two oesophageal bulbs. 

 The male has two equal spicula. 



Genera : Diplogaster, Mononchus, Khdbditis, Tylenclius, Anguil- 

 lula, and many others. 



Many species of this family live in humus or decaying matter ; 

 others live on, or are parasitic in, plants ; some, such as Anguil- 

 lula aceti, which is found in vinegar and in paste, live in organic 

 fluids. 



The part played by the presence of these Nematodes in the 

 soil is not thoroughly understood ; sometimes they occur in great 

 numbers, and even when not directly parasitic in plants, probably 

 do them much damage. Cobb * has recently described from 

 Australia and Fiji over eighty species, one-half of them new, which 

 occur mostly in the earth, and many of them among plant roots. 

 They frequently crawl up on to plants, especially on to seedlings. 

 An instance of this is given as follows : " The edible part of three 

 bunches of nice-looking celery bought of a Chinainau in Sydney 

 was cut off as far up as it was tender, nearly to the first leaflets. 

 It was washed by hand in a tin dish in tank water, free from 

 Nematodes. The washings gave about '200 to 300 Nematodes, 

 belonging to five different genera." 



It is very probable that many of the free-living forms which 

 have received distinct specific names may ultimately turn out to 

 be but stages in the life-history of some -of the parasitic species. 

 1 Macleaij Memorial Vol. Sydney, 1893, p. 253. 



