12 A MANUAL OF ZOOLOGY 



representing the forms of zoolds. Can a feeding zooid be 

 distinguished from a reproductive hydranth at this stage? 

 From the study of the hydra one can gfet a good idea of 

 the life process in this form. Several other forms of 

 hydroids will be furnished for study and comparison. 



PHYLUM ECHINODERMATA 



Asteroidea (Starfish) 

 What' is the general shape? Are there any variations 

 in different specimens? The under surface is known as 

 the oral, and the upper surface as the aboral surface. 

 Make drawings of both_ surfaces.- Whence the common 

 name of theTSimalT Examine and compare several speci- 

 mens for size and color. The central part of the body is 

 called the disk. Find the madreporic body on one side of 

 the disk. The bivium is formed by the two rays that touch 

 'the madreporic body. 'The other three form the-trivlum. 

 The anterior ray is the one opposite the madreporic body. 

 Note any differences in any of these rays. At this point 

 soak a medium sized specimen in dilute KOH for a. few 

 hours and carefully clea6 the flesh of! with a brush. This 

 will leave the skeleton which will be left to dry for future 

 use. 



Examine the spines as to shape, and size. Are they 

 movable? Note any differences in the spines around the 

 mouth (IVIoutli Papillae). Remove a small portion of the 

 skin and examine it under the microscope. Find the 

 ciliated columnar epithelium. The aboral tentacles will be 

 found at the base of the. spines. Around the mouth find a 

 membrane, the peristome. On the oral side of the rays 

 extending the entire length will be found the ambulacral 

 grooves, which contain the ambulacral feet. Pull off a foot, 

 make cross and longitudinal sections, then examine each 

 carefully for structures. Note the disk on the distal end, 

 and the opening through the center. Note the arrangement 

 of the muscles. Carefully pull oft some of the feet and find 

 a membrane stretched across the deeper part of the groove. 

 Above this will be found the radial water tube. A demon- 

 stration of the water vascular system will be made on 

 injected specimens. 



