86 MORPHOLOGY OF INVERTEBRATE TYPES 



Inclosed in the testis is a rachis similar to that in the ovary 

 and the sperm cells are grouped around it. The rachis is not 

 as long as the entire terminal portion and that part of the 

 thin tube, which is free from the rachis may be termed vas def- 

 er ens. The central portion is much shorter and thicker. It is 

 the vesicula seminalis. The end portion is again much thinner 

 and quite short, being no more than seven or eight millimeters 

 long. It has a musculature of its own and serves as ductus 

 ejaculatorius. 



In the immediate vicinity of the ejaculatory duct are two 

 pouches. They open into the cloaca, dorsal to the intestinal 

 canal, and contain two chitinous bristles or spicula which serve 

 as organs of copulation. 



Development. The fertilized eggs develop directly and 

 the shell protects the embryo from desiccation or climatic 

 changes. When swallowed with water or vegetables, the embryo 

 leaves the egg in the stomach of the host and matures in the 

 intestine. 



Instructions 



1. Put a female Ascaris into a dissecting tray with water and 

 examine the anterior end with the aid of a lens. Make a drawing 

 showing the ventral view of the anterior end. Label lips, ventral 

 line and excretory pore. 



2. Open the specimen by a longitudinal slit which should be 

 made parallel to and halfway between the dorsal and left lateral 

 lines. Pin down the body wall. Make a full page drawing 

 showing oesophagus, intestine, rectum, phagocytic organs if 

 visible, vulva, vagina, uteri and oviducts with ovaries. 



3. Open a male specimen in the same manner. Show in the 

 drawing the digestive organs, ductus ejaculatorius, vesicula 

 seminalis and testis with vas deferens; also the spicula. 



4. Examine prepared slide with a cross-section through the 

 nervous ring under low power (50 diameters) and make a drawing 

 showing all parts. 



