92 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



When they have a length of 4 mm., a is expressed by 

 19, P by 3, and 7 by 15. The tail of young larvae of this 

 size is still conical (PI. V, fig. 3 h), and terminates in an 

 acute point. The cuticula is finely striated; the lateral 

 membrane very conspicuous, presenting itself as a narrow 

 line, the width of which is only one fifteenth of the body- 

 diameter. The lips of the head are already conspicuous, 

 and the pharynx already almost as long as in the adult 

 individuals, but it is considerably narrower ; the width of 

 the pharynx, indeed, inclusive of its wall, measures only 

 one-ninth of its length, so that it appears to be only 

 nearly half as wide as that of the full developed worms. 

 The oesophagus presents already the same form as in 

 the latter ; the median bulb is well developed, as is also 

 the posterior, the length of which, however, still only 

 measures one-seventh (instead of one-sixth) of the distance 

 between the mouth and the extremity of the oesophagus. 

 I observed already in this specimen the oval rudiment of 

 the genital organs, which was 13 /^ long. In another young 

 larva, 0'44 mm. long, the said rudiment had already a 

 length of 18 /^. Besides by the striated cuticula, these 

 larvae differ at this size by the pharynx being narrower, 

 and by the different shape of the tail. 



Explanation of the Plates.* 



Plate III. 



Fig. 1. Aphelenchus tenuicaudatus, n. sp., ova-bearing 

 female, 0'95 mm. long, X the elongated gland, -f^; la, 

 anterior oesophageal portion of the body of another female 

 individual, 0*9 mm. long, X the ventral excretory pore, 



* When the contrary has not been stated, the figures have been drawn in 

 the usual lateral position of these worms. 



