158 Agricultural Gazette. 



Structure of the Worm. 



The worm is at once seen to be irregularly flask-shaped, the neck of the 

 worm corresponding also to the neck of the flask. _ In other words, the 

 large spherical portion is the posterior part of the animal, and the narrow 

 and more or less curved portion is the anterior part. The anterior part 

 terminates in a narrow head, presenting an opening, the mouth. _ The 

 posterior part, or abdomen as we may call it for the present, terminates 

 at its e.xtremo posterior point, v, Pig. 1, in a largo 

 opening, which is not the anus, as might be expected, 

 but the vulva or sexual opening. The outer covering 

 of the worm consists of a transversely-striated trans- 

 parent cuticle, the strisc being most clearly visible in 

 the neighbourliood of the head. The mouth-opening 

 is surrounded by three very obscure lips, behind 

 which is a mouth-cavity containing a characteristic 

 spear. This spear, which terminates posteriorly in 

 three knobs and is capable of being thrust forth and 

 withdrawn, usually lies with its point slightly behind 

 Fio. 1.— gall-wokm the lips. Leaving the mouth cavity, the food passes 



(T. arenaritts). through a chitinous tube into a prolate, highly mus- 



8.4e"inM^c "rovvahTtho cular bulb and thence through a short tube it passes 

 fita™9 Iii^bL 'ne'ntotton*"" '"''" ^^^^ intestine, if such still exist. (As will be 

 the^eKg'x i^oo-"™ vulva or explained farther on, the intestine has a remarkable 

 ofthe'e"'""""''' ' *' '''*""°"'^ way of disintegrating.) The dimensions of the above- 

 ^''^' mentioned organs are as follows : — ^Ta ken as a whole 



they occupy about one-sixth the length of the entire worm, and consti- 

 tute the oesophagus. Of the entire length of the oesophagus one-fourth is 

 taken up by the median bulb, one-twelfth by the spear, one-sixth by the 

 portion behind the bulb, and the remainder by the chitinous tube which 

 leads from the moulh cavity to the bulb. 



Further examination discloses other interesting points, but we must post- 

 pone their considerat'on until wc have examined the young worm from which 

 this sac-like, flask-shaped form has originated. This course will lead us 

 through a series of researches which it is not worth while to detail in full. 

 Suffice it to say that, on returning to the slice of potato, smaller specimens 

 than that just clescribed will be discovered, this discovery will be followed by 

 finding yeib smaller ones, and so on until we arrive, step by step, at the con- 

 clusion 'that the large flask-shaped worm entered the potato as an exceed- 

 ingly small worm of a totalli/ different shape. A search in the soil, if 

 conducted in a proper manner, soon discovers this minute worm, — that is, 

 the young or larva of the adult flask-shaped form. 



The larva; as taken from the soil present themselves as slow-moving, trans- 

 parent worms of the form shown in I Figs. 1 and 2, and have the following 

 dimensions :* il — aVi-i^Jo^a d '45 mm. The cuticula is devoid of hairs and is 

 traversed by about 500 transverse stri*. The neck is cylindroid to opposite 

 the base of the buccal cavity, but thence to the mouth convex-conoid. 

 There are no cephalic seta;, and but the faintest indications of a lip region. 

 There are no definite organs of vision, and apparently no lateral organs. 

 The spear, which is three-bulbed at its base, is generally drawn back so that 

 its point is removed half the spear-length from the mouth. (See II Pig. 2.) 

 That portion of the ujsophagus in front of the median bulb is narrow but 

 of rather uncertain width, and is lined throughout with thick chitinous 



* For the dimensions the reiwler will please give preference to the formula, I Fig. 2 beinjif'considcrabl.v 

 t«o wide though otherwise correct. For an explanation of the formula see page 131, Vol. I, Tart 1, 



