C(ELELMINTHA. 101 



verses the whole length of the body, and terminates by an anal 

 aperture at the extremity of the tail. 



(135.) The nervous system of the Linguatula is distinctly de- 

 veloped. It consists of a central ganglion, situated beneath the oeso- 

 phagus^ from which eight pairs of nervous filaments proceed in dif- 

 ferent directions : of these the greater number are distributed to the 

 parts immediately around the mouth, but the posterior pair (o, o), 

 which is by far the most considerable in size, runs backwards along the 

 ventral aspect of the body, taking first a wavy or serpentine course, 

 but afterwards becoming straight ; these nerves may be traced for 

 some distance until they are gradually lost in the integuments, to 

 which they are distributed. 



It will be seen that in such a condition of the nervous apparatus, 

 we have a type of structure decidedly superior to what has been 

 observed in any of the parenchymptous entozoa, and adapted to 

 the situation in which the Linguatula is generally found ; a situa- 

 tion which allows of considerable change of position, and of some 

 selection as regards the food which it imbibes. The muscular 

 movements, therefore, being more perfectly associated by the de- 

 velopement of nervous filaments, exhibit a greater energy of action ; 

 and although the nervous matter is not as yet sufficiently concen- 

 trated to allow of the possession of organs appropriated to the 

 higher senses, there is provision made by the developement of the 

 rudimentary sub-oesophageal ganglion for more delicate sensibility 

 in the neighbourhood of the mouth, adequate, no doubt, to the 

 perception and choice of such aliment as may be best adapted to 

 nutrition. 



(136.) The female Linguatula^ as is generally the case among 

 the dioecious entozoa, is considerably larger than the male. The 

 generative organs exhibit a peculiar arrangement, and form nu- 

 merous convolutions in the body, which are visible through the 

 semi-transparent integument (Jig. 43, 1). 



The ovary (Jig. 43, 2, g) is a narrow, minutely granulated 

 body, running along the two anterior thirds of the dorsal aspect of 

 the body. It terminates about half an inch from the head in 

 two capillary tubes (c c), which pass on each side of the stomach 

 and nervous cords, embracing them as in a ring. These two tubes 

 unite behind the mouth into a common canal or oviduct, through 

 which the eggs escape ; but, before their junction, each receives a 

 duct derived from a glandular sacculus (e, e), destined no doubt to 

 furnish some secretion essential to the completion of the ova. 



