OF THE XEMATOIDS, PAILVSITIC AXD ¥EEE. 631 



PLATE XXIV. 



Internal aspect of anterior extremity of Ascaris htmhricoides, slit open in the 

 mid-dorsal line (cEsophagus removed, muscles not represented, lateral bands 

 only in outline). Showing nervous system and so-called " vascular arch," 

 outlined with the camera lucida : — «, oesophageal band ; J, median group of 

 ganglion-cells; c, c, two submedian ventral groups, the cells of which are 

 mostly bipolar, connected with those of last group and with others, d, d, im- 

 bedded in the substance of the lateral bands; e, a large peripheral fibre which 

 was seen to pass in the cellulo-granular layer beneath the muscular bundles ; 

 f,f, nervi submediani; (/, g, nervi laterales; h,h, very large ganglionCJj-cells ; 

 i, i, bundles of fibres, going to the dorsal head-lobe, chiefly in connexion with 

 the lateral ganglion-cells; k, k, two distinct bipolar cells on each side; 

 I, I, lateral ventral head-lobes ; m, m, two halves of dorsal head-lobe ; 

 n, n, lateral bands; n', ventral median line; o, "vascular arch"; ^;, large gra- 

 nular cell in substance of wall of vessel on left side ; q, ventral pore, situated 

 in a plane external to the arch itself, with which it is connected by a single 

 outgoing tube. 



PLATE XXV. 



Fig. 1. Section through the middle of head-lobes and triangular pharynx of Ascaris 

 megalocejilmla. 



Fig. 2. Section of body of same immediately behind the head-lobes : — «, chitinous portion 

 of integument ; 5, cellulo-granular layer of same ; <?, c, c, commencement of 

 longitudinal muscles; d, large oesophagus, showing a trilobate form, with 

 thick walls, composed of transverse, radiating fibres, and large, triradiate lumen. 



Fig. 3. Section of same slightly anterior to position of nervous ring, showing a blending 

 of prolongations from lateral and median lines around the oesophagus, in 

 which are imbedded the anterior peripheral nerves ; letters a-d same as in 

 last figure; e, e, lateral bands; f,f, median lines. 



Fig. 4. Section of same (female) just posterior to tennination of oesophagus, and ante- 

 rior to the situation of genital organs ; parts similar to those described in 

 Plate XXIII. fig. 2, the most noticeable differences being the smaller size of 

 the lateral band and the greater distinctness of its contained tube, and the 

 alteration in form of the developments from muscle-cells (h, /«)*. 



Fig. 5. Section of female of same species through the rectum, slightly anterior to the 

 anal cleft : — a, structureless wall of intestine devoid of its cellular lining ; 

 b, contractile tissue in connexion with the lateral bands, surrounding the 

 intestine like a sphincter, and having imbedded in its substance (c, c, c) one 

 upper, large, and two lower, smaller, densely granular cells, similar to that 

 met with on the left side of vascular arch ; /,/, median lines. 

 * See ako Plate XXIII. fig. 16. 



