32 MORPHOLOGY OF INVERTEBRATE TYPES 



ductive cells are dehisced directly into the bell cavity and 

 through the bell-opening to the outside. The sexes are separate. 

 Fertilization is left to chance and takes place outside of the 

 body, in the water. 



Instructions 



1. Examine a specimen of Tima formosa in a finger bowl with 

 water. Make a half page drawing showing the paraboloid ex- 

 umbrella, velum, bell cavity, peduncle, manubrium with the 

 four lips, the four radial canals, gonads, circular canal, tentacles. 

 Determine the perradial, interradial and adradial planes. Label 

 all structures including the bulb and shaft of a tentacle, and the 

 planes. 



2. Cut off a piece of the margin with two tentacles and a por- 

 tion of the velum. Put it on a slide in glycerine, exumbral side 

 uppermost and examine under low power (50 diameters) without 

 a cover glass. Make a drawing showing the hollow bulbs of the 

 two tentacles, three protuberances and four statocysts. 



3. Cut off a piece of the velum and place it on a slide in a drop 

 of glycerine, subumbral side uppermost. Cover it up with a 

 cover glass and examine under high power (400 diameters). 

 Make a drawing showing the circular muscles. 



4. Examine in the same manner the shaft of a tentacle. 

 Make a drawing showing muscular strand, nematocysts, en- 

 doderm and cavity. 



5. Examine under high power the prepared slide with a radial 

 section through the velum and bell edge. Make a drawing show- 

 ing the circular canal, mesogloea, subumbral and exumbral 

 nervous rings and the two ectodermal layers of the velum with 

 the mesogloea between them, and the muscular fibres in the 

 subepithelial subumbral layer of the velum. 



