CAMPANULARIAN HYDROID. 35 



V. Search among the tips of the branches of a colony 

 for the various .stages in the process of formation of a 

 hydrant h by budding, , 



and notice : 



a. A stage in which 

 the bud is a simple, 



n earl y cylindrical ** 



knob at the end of a FlG ' 20 - 



branch (Fiij. 16). The FlG ' 2(X ~~ A dischar S ed nematocyst, mag- 

 nified three hundred and fifty diameters. 



coenosarc is in contact 



with the thin investing layer of perisarc (Fig. 16, a), 

 and its distal end is made up of a thick layer of ectoderm 

 (Fig. 16, b) and a mass of loose endoderm cells (Fig. 

 16, c). At a very early stage the cavity of the stem does 

 not extend into this muss. 



b. A stage in which the bud (Fig. 17) is club-shaped, 

 the perisarc at the tip of the stem very thin, while the 

 ectoderm is very thick. The body cavity (Fig. 17, d) 

 no\v extends into the bud, and the endoderm cells 

 (Fig. 17, c) form a true inner layer. The coenosarc 

 has begun to separate from the perisarc at the sides, and 

 the outline of the body of the hydranth can be recog,- 

 nized. 



c. In a more advanced stage (Fig. 18) the shape of 

 the body is well marked, and the coenosarc is more free 

 from the perisarc, which still entirely covers it. 



d. In a more advanced stage the perisarc is ruptured 

 and expanded to form the hydrotheca, and the manubrium 

 and budding tentacles can be seen. 



e. Make a sketch showing the various stages in the pro- 

 cess of budding. 



f. Notice that in the living specimen the particles of 

 food are carried through the hydrocaulus into the body 



