30 LABORATORY DIRECTIONS IN 



where are the germ cells? Are they of more than one kind? Examine 

 preparations of ovary and of seminal vesicles to secure facts for the 

 answers to these three questions. How many kinds of somatic cells 

 are there? Compare their distribution over the body with their dis- 

 tribution in Hydra. Which arrangement appears to you the more com- 

 plex? The more specialized? What are organs? Systems? Does 

 Hydra have any approach to organs? If so, where? 



B. AGGREGATIONS OF MANY-CELLED INDIVIDUALS 



7. Bugula belongs to a group of animals known as Bryozoa. They 

 are found in both fresh and salt water. Bugula is a salt water form. 

 Study a branch in a watch glass. Note the plant-like form. It lives 

 attached to rocks and other objects in the water. 



Study the method of branching. In a stained branch on a prepared 

 slide, note how the individuals are arranged. 



From a prepared slide examine a favorable individual with a low power 

 of the microscope. Note the transparent sheath surrounding the indi- 

 vidual, the tentacles surrounding the mouth, and the form of the re- 

 mainder of the body. Are all individuals alike? 



Sketch several individuals including the sheath as seen under the 

 compound microscope. 



8. Obelia is an animal related to Hydra (a member of the phylum 

 Coelenterata). It grows in plant-like colonies on wharves and rocks 

 in salt water. Under the dissecting microscope note the tree-like form 

 of a single branch. Specimens in watch glasses or mounted permanently 

 on slides may be used for this purpose and for the identification of the 

 kinds of individuals and their parts indicated below. Use the compound 

 microscope for parts of this study. 



8a. Hydranths or zooids, bearing tentacles, are located at the ends 

 of the branches. Each hydranth is enclosed in a cup-like sheath or 

 hydrotheca which is a continuation of the tough membranous covering of 

 the whole colony (the perisarc). 



In an expanded hydranth note the body with the hypostome, an elon- 

 gated projection in the midst of the tentacles. The fleshy continuation 

 of the hydranth into the stalk is the ccenosarc. The cavity in the body 

 of the hydranth continues through the coenosarc. 



86. Gonangia (singular gonangium), club-shaped individuals usually 

 found in the angles between the hydranths and the main stalk. Note 

 that they have no tentacles, hence can capture no food. How can they 

 be nourished ? The sheath forming the outer portion of the gonangium is 

 the gonotheca. The fleshy core of the gonangium is the blastostyle. 

 Upon the sides of the blastostyle find 



8c. Medusce, here in an immature form, mere rounded projections. 

 In the larger ones, the beginning of the tentacles may be seen at the margin 



