OF THE NEMATOIDS, PAEASITIC AND FKEE. 581 



sacculi (Plate XXVII. fig. 22), in much the same position as it was represented to exist 

 by Carter*. 



In the Nematoids generally, the intestine is bound to the parietes of the body by 

 more or less developed retinacula, which are usually delicate prolongations from the 

 longitudinal muscles. 



The cellular layer lining the intestine has in all probability a glandular function to 

 perform, and its share in the process of assimilation may perhaps entitle it to be looked 

 upon as possessing a rudimentary hepatic function. Such seems to be the general opinion 

 as to its nature. 



With regard to the food of the parasitic Nematoids, a great difference exists according 

 to the particular parts of the body of their respective hosts which they are in the habit 

 of frequenting, and it seems reasonable to expect that differences in organization might 

 be met with amongst these species, in a measure coincident with the degree of elaboration 

 of the fluids upon which the respective animals feed. We seem to be able to recognize 

 this to a certain extent, since in Prosthecosacter inflexus, inhabiting the heart and vascular 

 sinuses of the Poi-poise, and consequently drawing its nourishment from a fluid already 

 much elaborated, I have found a low development of the glandular structures of the 

 body ; whilst in the Ascarides, such as A. spiculigera from the stomach of a Cormorant, 

 or A. osculata from the intestines of the Seal, feeding upon less elaborated materials, 

 we have seen the enormous development of the glandular hepatic lining of the intestine ; 

 and in A. lumbricoides we meet with an enormous development of the glandular portions 

 of the muscles in the form of bladder-like prolongations, constituting the " appendices 

 nourriciers " of Cloquet. 



In the " Monograph on the Anguillulid8e"f , I have mentioned a few particulars con- 

 cerning the food of the free Nematoids, and have also alluded to the occasional large 

 quantity of fat met with within the alimentary canal of these animals, apparently as a 

 primaiy product in the process of assimilation. 



GLANDULAR SYSTEM. 



The glandular system, under various forms, is extremely well developed in the Nema- 

 toids, and seems to fulfil a most important function in their economy. 



A series of floating gland-cells exists in variable quantities suspended in the fluid 

 contents of the general cavity of the body, which may be considered analogous at least 

 to the blood-cells or corpuscles of higher animals. The fluid in which they float is 

 mostly colourless, though in some Nematoids, as in Syngamus trachealis, it is of a blood- 

 red colour. The cells themselves vary much in size as well as in number. In Ascaris 

 himbricoides they may be found in the fresh dead animal aggregated together in minute 

 masses in the cavity of the body, the cells themselves being about ^^575^" in diameter 

 and of a somewhat light-olive colour (Plate XXIII. fig. 12). In many of the free 



• Annals of Nat. Hist. Ser. 3, vol. iv. (1859) pi. 1, fig. 6. t Loe. dt. p. 84. 



