UNSEGMENTED " WORMS. 



the food consists chiefly of juices either from a hving host 



or from putrefying organic matter, it is not surprising to 



find that the alimentary canal has usually but a narrow 



cavity. In some forms, e.g., Sphceriilaria 



from the bee, it degenerates altogether. 



Normally it consists of three parts, a fore 



gut or cesophagus, lined by the inturned 



cuticle, a mid gut or mesenteron of endo- 



dermic origin, and a usually short hind gut 



or rectum, lined by the cuticle. When 



the external cuticle is shed, so is that of the 



fore gut and hind gut (cf Crayfish). 



Body Cavity. 



A ccelome is developed and contains 

 a clear fluid, which probably discharges 

 some of the functions of the absent blood. 

 There are no amoeboid phagocytes. 



Exa-etory System. 



Imbedded in each lateral line there is a 

 long tube containing clear fluid, probably 

 drained from the surrounding tissues. The 

 two longitudinal tubes unite anteriorly, 

 and open in a ventral excretory pore near 

 the head. 



Reproductive Svste/ii. 



The sexes are separate, except in A/igio- 

 stomum which is hermaphrodite and self- 

 fertilising. In the male, the testis is 

 usually unpaired, — a coiled tube gradually 

 differentiating into vas deferens, seminal 

 vesicles, and ejaculatory duct. The genital 

 aperture is close to the anus, and beside it 

 there are sensory papillos, and often spicules, 

 and peculiar membranous folds of varied 



Fig. 59. — Illus- 

 trating the struc- 

 ture of a Nematode 

 ( O.xyiin's). (After 

 G.\LEE.) 



"!., Mouth : c, cu- 

 ticular ring ; a'., ceso 

 phagus ; B., bulb con 

 taining teeth ; /., in 

 testine ; T., testis 



form which constitute what is called the t'.<i'.,v.i's deferens ;.vi, 

 copulatory "bursa." The spermatozoa have "'"'"' '"'"' ■■" '""'• 

 not the typical form, and are sluggish. In the female, 

 the ovary is a single or paired tube which passes grad- 



