552 DR. H. CHAELTON BASTIAN ON THE ANATOMY AND PHT8I0L0GT 



and thickly arranged in transverse rows in A. echinata ; exist as an innumerable quan- 

 tity of recui-ved hooks on the anterior part of the body of a species of Spiroptera found 

 by Mr. Bellingham in Anas tadoma ; as circular groups of palmate spines in Gnatho- 

 stoma spinigerum* ; and as acute recurved spines arranged in a quincunxial manner on 

 the anterior part of the body of Hystrichis tricolor. In Trichosomum tomentosum, 

 DuJARDiK found a portion of the body clothed with a multitude of very minute, 

 spreading, hair-like processes. Amongst the free Nematoids, and more particularly the 

 marine species, hair -like processes or seta? are very abundant, existing principally as 

 circlets round the head, and in linear series on the ventral region of the caudal extremity 

 of many males. They are often scattered more sparingly over other parts of the body, 

 and altogether seem to reach their maximum development, so far as I have observed, in 

 Sphcerolaimus hirsutusf. These setae of the free Nematoids seem to take the place of 

 the spines in the parasitic species, as the latter structures are not met with in either 

 marine, land, or freshwater representatives. 



Papillce and Suckers. — These organs, either separate or combined, are of very common 

 occurrence in connexion with the integument, both among parasitic and free Nematoids. 

 They exist in two principal situations — around the head, and about the caudal extre- 

 mity of many males. Some of the organs met with in the latter situation are undoubt- 

 edly suckers, though with regard to other structures, both in this region and around the 

 mouth, it seems by no means clear whether they should be considered simply as papillae, 

 or whether they are also suctorial. 



The cephalic papillae can be well studied in Ascaris lumbricoides, though their number 

 and arrangement appear to be nearly the same in all the species of this genus. Two 

 exist on the dorsal head lobe (one on each side), and one in the middle of each latero- 

 ventral lobe (Plate XXII. figs. 14 & 19). In A. lumbricoides they present the following 

 structure; externally there is a convex projection of the chitinous envelope with a 

 minute perforation in its centre, running down to a depression in the apex of a well- 

 marked, bluntly conical projection of the deep cellular layer (Plate XXII. fig. 17), which 

 with some fibres (mainly nerves 1) constitutes the central parts of these lobes J. These 

 latter are essentially skin development formed around and enclosing the triradiate 

 mouth, and do not contain well-marked prolongations of the great longitudinal muscles 

 as stated by Kuchenmeistee. The papillae which they bear, therefore, may be simple 

 tactile organs, or they may be partly suctorial. In Spiroptera obtusa there are six 

 cephalic lobes, each of which bears a single papilla. Well-developed papillae exist 

 around the mouth in the genera Cucullanus and Sclerostomum, and more simple ones 

 in the genera Dracunculus and Filaria. Amongst the free Nematoids they are best 

 developed in the genus Enqphcs. I cannot say, however, whether the cephalic papillae 

 are perforated in the same way in the members of these other genera as I have found 

 them to be in those of Ascaris. 



* Diesing's Cheiracantlms robustus. t Trans, of Linn. Soc. vol. xxv. pi. 13, fig 192. 



t " Cock's-comb-like structures." — Kuchenmeistee (Syd. Soc. Transl.), p. 411. 



