36 



GUIDE TO THE STUDY 



Cross-sections. — Examine prepared slides of cross-sections of 

 Ascaris lumbricoides or of a related species. Under low power 

 make a drawing showing the body wall, the alimentary canal, 

 reproductive organs, and the dorsal, ventral, and lateral lines. 



Using high power, make a drawing showing the body wall: the 

 cuticle with its various strata, the hypodermal layer from which 

 the cuticle is a derivative, and the single layer of longitudinal 



Fig. 14. — Migrating larva of Ascaris lumbricoides in liver of guinea-pig 6 days 

 after feeding. (Orifj.) 



muscles. Each muscle possesses a protoplasmic core with a 

 nucleus, and a contractile sheath. If possible, find a section cut 

 through the nucleus to include in your drawing. Each muscle 

 cell, or fibril, is enclosed in a thin connective sheath the nuclei 

 of which are often discernable. 



Development. — The eggs of Ascaris lumbricoides, as of many 

 Eunematoda, develop directly, without the necessity of an 

 intermediate host. In the course of development the larvae 

 undergo a migration through the liver and lungs of their new 



