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ON THE ANGUILLULIDE. S1 
lines which have so long been a puzzle to anatomists. I have also detected these 
cutaneous pores in several of the parasitie Nematoids. In many species the integument 
is provided with setze around the head, and more sparingly on other parts of the body ; 
occasionally it is developed into papillæ 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 Diatomacee, 
and in one case I saw two or three Vorticelle. In Spira parasitifera 1 have frequently 
found specimens of a stalked fan-shaped diatom, probably belonging to the genus 
Echinella, as well as Vorticelle, 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 esophagus. This latter 
is often distinetly 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 cesophagus 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 cesophagus 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 mesenterie envelope, between which is situated a 
uniform layer of cells, containing light or olive-coloured fat-particles, probably having 
a rudimentary hepatie 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; but, 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 Leptosomatum figuratum I have measured 
one of this character of an elongated oval form, whose length was three times the 
breadth of the parent body. In Dorylaimus stagnalis, Dujardin, however, they are 
much smaller, admitting two or even three abreast within the uterus. In most of the 
VOL. XXV. M 
