NEMATOMORPHA STRUCTURE 



I6 5 



at each end ; the male, however, is easily distinguished, from the 

 female by its forked tail (Fig. 89). Not unfrequently a con- 

 siderable number are found inextricably tangled together into a 

 knot, and the name of the genus refers to this fact. Where 

 numbers have suddenly appeared in water hitherto free from them, 

 legends have sprung up which attribute their presence to a rain 

 of worms ; in reality they have come out of the bodies of Insects 

 in which they are parasitic for the greater part of their life. 



The genus Gordius passes through three distinct stages, of 

 which the first two are larval and parasitic ; the third is sexually 

 mature and lives in water. The second larval stage closely 

 resembles the adult, but the reproductive organs are not developed. 

 The following account of the structure of this larval form and 

 of the adult is in the main taken from von Linstow. 1 



The whole body is covered with a well-developed two-layered 

 cuticle, which in the adult is marked out into areas, and bears 

 numerous minute sensory bristles, which are especially developed 

 in the neighbourhood of the cloaca of the male. Beneath this 

 is a hypodermis which differs markedly from the sub-cuticle of 

 Nematodes, inasmuch as 

 it consists of a single 

 layer of polygonal nucle- 

 ated cells. Within this 

 lies a single layer of 

 longitudinal muscle-cells, 

 which differ from the cor- 

 responding layer of Nema- 

 todes in having that 

 part of their medulla 

 which is not surrounded 

 by the contractile por- 

 tion directed outwards 



towards the hypodermis, Fl - 83.-Transverse section through a young male 



J r ' Gordius tolosanus Duj. (From von Linstow.) 



and not inwards towards Highly magnified, a, Cuticle ; b, hypodermis ; 



thp lWhr oaw+xr c, muscular layer ; d, parenchyma ; e, alimentary 



Wie UOliy-ca\ 1I} . canal . ^ nervous sys t era ; g, cells of the testis. 



The body is in the 

 younger stages practically solid, the interior being filled with 

 clearly defined polygonal cells which are arranged in definite 

 rows ; in later life certain splits arise in this tissue which sub- 



1 Arch. miTcr. Anat. Bd. xxxiv. 1889, p. 248. 



