ON THE ANGUILLULID^. 81 



lines which have so long been a puzzle to anatomists. I have also detected these 

 cutaneous pores in several of the parasitic Nematoids. In many species the integument 

 is provided with seta3 around the head, and more sparingly on other parts of the body ; 

 occasionally it is developed into papillae around the mouth ; and, besides the caudal 

 sucker before alluded to, many of the males are furnished with a varying number of 

 ventral suckers. Ehrenberg records the fact of his having observed Anguillula recti- 

 Cauda cast its skin. I have seen evidences of the same thing in many species, and 

 suspect that, during the period of growth of the free Nematodes, it is the rule. In some 

 few species, the integument appears to be glutinous. Thus Oncholaimus vulgaris, from 

 marine mud, has always adhering to its surface minute particles of sand and Diafomacece, 

 and in one case I saw two or three T'orticellce. In Spira parasitifera I have frequently 

 found specimens of a stalked fan-shaped diatom, probably belonging to the genus 

 Echinella, as well as VorticeUce, attached to the integument. Some few species, too, of 

 the genus Chromadora, from marine mud, have been found enclosed in a tube like that of 

 the Sabella, composed of agglutinated sand-particles. 



The alimentary canal commences wih a terminal rounded mouth, either opening into 

 a dilated pharyngeal cavity or communicating at once with the ossophagus. This latter 

 is often distinctly muscular, and has sometimes a pretty equal calibre throughout, whilst 

 at others it is provided with one or two rounded or oval muscular swellings. The 

 posterior one is occasionally provided with a few horny plates in its centre, and has 

 generally been described as a stomach, though, I think, erroneously, since it seems to 

 perform none of the functions of a stomach : it is not a receptacle for food, and the 

 swelling is due to an increased muscularity of the walls of the oesophagus at this point, 

 rather than to a dilatation of its central cavity. The structure seems to me to partake 

 more of the nature of a valvular apparatus, partly facilitating the swallowing of food, 

 and partly preventing the regurgitation of the freely moving and fluid contents of the 

 intestine proper, during the rapid movements of the animal. This oesophagus is divided 

 by a well-marked constriction from the intestine, which continues nearly uniform in size 

 throughout the remainder of its course, terminating by a curved anal cleft on the 

 ventral surface of the body at a variable distance from the posterior extremity. It is 

 made up of a central tube and a mesenteric envelope, between which is situated a 

 uniform layer of cells, containing light or olive-coloured fat-particles, probably having 

 a "rudimentary hepatic function. The arrangement of these cells and their contained 

 granules is sometimes so regular as to give a distinctly tessellated appearance to the struc- 

 ture ; whilst, at others, the intestine merely appears covered with a layer of irregularly 

 disposed fat-particles, the containing cells being invisible, and their contained particles 

 not definitely aggregated. 



Some of the free Nematodes are viviparous ; bu.t, as before stated, most are oviparous, 

 the ova being large and proportionally few in number. In many species they are so 

 large as singly to distend the body ; and in Leptosomattim figiiratum I have measured 

 one of this character of an elongated oval form, whose length was three times the 

 breadth of the parent body. In Donjlaimus stagnalis, Dujardin, however, they are 

 much smaller, admitting two or even three abreast within the uterus. In most of the 



VOL. XXV. M 



