ENTOZOA. 163 



ity a short tubular penis ; sheath armed with minute retroverted spines ; tail 

 straight and bluntly pointed. 



Measurement. Male. !"' long; female, 2'" long. Eggs ? | " to f^". 



Habitat. Head of large intestine. 



Ascaris. Body subcylindrical, subequal at either end, rarely armed. Head 

 subconical, continuous with body. Mouth terminal trilabiate, when closed 

 assuming the form of a triangle. Caudal extremity naked or winged. Penis 

 filiform, enclosed in a bipartite sheath with linear branches, sometimes very 

 long. Genital pore of the female in front or posterior part of the body. 

 Rarely viviparous. (Diesing.) 



A. lumbricoides, Linnaeus. Body smooth, fusiform and elastic, marked 

 by numerous fine transverse rings, and attenuated gradually toward either 

 extremity, the anterior terminating in a much-produced tripapillated mouth, 

 the posterior in a bluntly pointed tail ; female much broader than the male, 

 having a diameter of \ of an inch and a circumference of f '"; male repro- 

 ductive organs furnished with a double speculum or penis, extremity of body 

 arcuate; female genital pore at lower part of the anterior half of the body. 

 Measurements. from 4 "-6" long; $ 10"-14" long. (Cobbold.) Intes- 

 tine terminates in a cloacal cavity which opens by a transverse slit at a short 

 distance from the end of body. Skin of two layers: external, chitinous; in- 

 ternal, granular. Spermatic tube 3' long in most specimens; oviducts 4'. 

 Gullet long, somewhat triangular, with thickened walls ; very narrow at its 

 commencement, it gradually increases in size, and is then suddenly con- 

 stricted. The stomach consists of two globular dilatations ; its walls are 

 thinner than those of the ossophagus. The intestine is straight, and presents 

 some slight bendings ; it becomes narrower toward the vent. The canal ap- 

 pears to be surrounded by white vesicles suspended in the cavity of the body. 

 The anus is near the posterior extremity of the animal, and has the form of 

 a transverse opening. The nervous system composed of two white cords 

 running along the sides of the body ; no ganglia apparent. The testicles 

 and spermatic cords are filiform, and surround the alimentary canal. Vagina 

 narrow, uterus short, provided with long flexible horns. These become con- 

 tinuous with the ovaries, which are long, and twisted upon themselves 

 around the alimentary canal. 



Development imperfectly known. Eggs are deposited in water. The em- 

 bryo subsists for a long time active within the egg capsule. (Moquin-Tan- 

 don.) 



Habitat. Small intestine. 



A. mystax, Rudolphi. Moderate size ; alaeform appendages, one on either 

 side of head ; mouth trilobate. Male 2%'" long ; tail arcuate ; body coiled ; 

 spicules 2- 5 y " long. Female 4 inches long ; less coiled. Eggs measure 



si/'- 

 Habitat. 



