J^ew South Wales. 



159 



walk. The ellipsoidal median bulb is situated just in 

 frout of the somewhat oblique ncrve-riiig and is con- 

 nected with the smaller and weaker posterior bulb or 

 swelling by a canal one-sixth as wide as the adjacent 

 portion of the neck. While the median bulb and all of 

 the oesophagus in front of it are characterized by 

 possessing a thick, transparent, horny lining of the same 

 composition as the spear, the posterior portions of the 

 oesophagus are nearly devoid of such linings. If, there- 

 fore, the a'sophagus be divided by a transverse cut just 

 behind the median bulb it is separated into two dis- 

 similar parts, of which the anterior is the stouter and 

 better developed. The pellucid alimentary canal is two- 

 thirds as wide as the body, and its cells are closely 

 packed with coarse spherical granules. The unicellular 

 ventral gland empties, by means of a long chitinous duct, 

 through the porous cxcretorius just opposite the com- 

 nienceuient of the intestine. The lateral fields are one- 

 fourth as wide as the body and have a double structure, 

 presenting four parallel longitudinal lines. The tail is 

 conical from the inconspicuous anus. There arc no 

 caudal glands, and the terminus is pointed. 



Prom this description it is evident that, so far as the 

 larva) are concerned, this worm must be referred to the 

 genus Tylenchus, and it may as well here be added that 

 the adult form presents no features that alter the decision 

 thus made from the structure of the larva. 



We have now to trace the development of the larvas. 

 I have found the larvas in the soil sent from Pretty Gully 

 Scrub. That they are abundant in the soil there is 

 beyond doubt. I found them in tlie first particle ex- 

 amined, but have not made sufficiently careful search to be able to give a 

 precise notion of their exact abundance. It is hero to be noted that the soils 

 examined were forwarded by mail, reaching my private laboratory after being 

 several days on the way, and when finally examined were quite dry and 

 caked. It is certain that the larv« can endure a short desiccation, for those 

 contained in this soil revived on being placed in water, and furnished the 

 specimens from which the foregoing description was taken. This ability to 

 withstand drying is a characteristic of many Nematode species. The young 

 of some species revive after being kept in a dried-up state for several years. 

 This fact will be referred to again in speaking of contagion. 



It is necessary to assume that the larvip make their way into young roots 

 at an early stage of their existence. How long they may live in moist soil 

 without entering roots of living plants I am unable to say. It is not 

 impossible that it may be a long time, but for two reasons it is improbable. 

 First, I have found no specimens living free in the soil that measured above 

 •54 millimetres, but have on the other hand found specimens inside the 

 tissues of roots that measured not more than that, although the diameter 

 was relatively greater than in the free-living larva>. Such a specimen is 

 shown in Fig. 3. Its dimensions were as follows: \i % '.j'5 ic'i "'o- ■ '42 mm. 

 Secondly, the entrance into root tissues is accomplished at an early age in 

 an allied species. 



The mecnanism by means of which the larva) make their way into the roots 

 and rootlets of plants, namely the spear and the median oesophageal bulb, 



Fio. 2. T. arenarius. 



I, the larva X 200 ; II, 

 liead of same x 900 ; III, 

 bit of the middle of tlie 

 body X (iOO ; IV shows 

 at the centre tlie actual 

 len^tli of the womi ; s, 

 the spear ; b, the bulbs ; 

 n, the nerve-ring ; i, the 

 intestine ; c, cuticula ; /, 

 lateral fields ; a, anus. 



