J{ew South Wales. 165 



It will be Been that the worm under consideration harmonizes with this 

 characterization with slight exceptions. The male of the present worm has 

 no bursa ; but I cannot think this an objection to calling it Ti/lenchus. The 

 bursa is very variable in Tylenchus, msomn cases enveloping the tail completely, 

 and in others extending only a short distance on either side of the anus, being 

 in the latter case quite rudimentary. That it should fail completely cannot 

 be regarded as even remarkable. Again the present worm presents a 

 history, not hitherto admitted in the genus Ti/lenchus ; but the remarkable 

 change to the flask-like form is due merely to the degeneration of the 

 digestive and muscular tissues on the one hand and an unusually luxuriant 

 growth of the sexual organs on the other. The morphology of the animal is, 

 it is true, thus obscured, but it is not materially changed. One never thinks 

 of excluding certain species of Ithahdilis from (he genus to which they 

 properly belong, merely because the young, as is often the case, finally rupture 

 the uterus, and, entering the body cavity, devour its contents, and by growth 

 finally give the body-wall of the mother-animal a bloated appearance. These 

 two facts, the absence of the bursa, and the jieculiar life-history consequent 

 upon a truly parasitic life, are the main grounds for placing our worm in a 

 genus separate from 'Ti/lenchus. Against these two objections, which are in 

 reality slight, may bo sot up a vast array of arguments based on the similarity 

 existing between it and I'yhnclms. Let us consider in detail the exact 

 proportions of a typical Tylenclms. For this purpose 1 iiave averaged the 

 lormulffi of twenty species of this genus. The males of some of these species 

 are as yet unknown, consequently I have first averaged the female forinulse, 

 and with the following results : — 



(1.) Average female formula when the sexual organs are single, }!° ; ''i' ^'.' ^ 1-23. 



(2. ) Average female formula when the sexual organs are double, 'f* \ '" -^ — 7— 1 '4. 



From the males which are known the following averages are obtained : — 



(3.) Average male formula when the female sexual organs are single, J^^ — ' ''3'° 32 "ta ^- 

 (4. ) Average male formula when the female sexual organs are double, 2 « ? '8 JJ M 05-8 -^ .gg^ 



Imperfect as these formula; are, on account of our incomplete knowledge 

 of many of the species, they serve to show at once the striking similarity 

 existing between the worm we have under consideration and tlie typical 

 Tylenclms. Compare the formula of the larva of the present species with the 

 above formula), remembering always that the comparison is between a larva 

 and adult forms, and that tho relative lengtli of tlie ojsophagus and tail 

 and all their component parts will in the larva decrease with age, as will 

 alec the relative width. It is evident at once that the resemblance is great 

 in any case, and will ultimately be greatest between the worm whose alhnity 

 we are trying to discover and those Tylciichi whose females have double 

 sexual organs. This is true, whether we compare the formula of our larva 

 with the female Ibrmuhc of Tylenclms or compare the formula of our adult 

 male with the male formula) of Tylenclms. This result is all the more sig- 

 nificant when we consider that the females of our species ultimately develop 

 double sexual organs, and that species with blunt tails are relatively much 

 more common in that group of Tylenchi whose females possess double sexual 

 organs. There is not the slightest doubt left in my mind that we liave here 

 to do with a Tylenclms belonging to the group with double female sexual 

 organs, which has, owing to a truly parasitic life, taken on some very 

 striking but truly slight new morphological characteristics. 



