BOUGAINVILLIA. 33 



gonophore and examine the developmental stages, (a) Some- 

 what irregular disc-shaped embryos with a variable number of 

 projections around the margin, the forming tentacles (6). 

 Older stages with the tentacles more developed and with disc- 

 or lens-shaped bodies in which the coelenteric cavity can be 

 easily seen, (c) Actinula stage. Essentially a small polyp. 

 Notice the number of tentacles, the position of the mouth, and 

 the method of locomotion. 



Actinulse kept in a covered watch-glass of sea-water will 

 attach and form the basis of new colonies. 



Make drawings of gonosomes, gonangia, and developmental 

 stages. 



7. The arrangement of the attached medusae is best seen in 

 sections. 



Sections show the same body layers as Hydra, and the 

 derivation of the medusa as an outpocketing of the wall of the 

 hydrant h is evident. 



Hargitt: The Early Development of Penneria tiarella. Arch f. Entwick- 



lungsmech., 18, 1904. 



Pearse: Reactions of Tubularia crocea. Am. Nat., 40, 1906. 

 Torrey: Biological Studies on Corymorpha. I. Jour. Exp. Zool., 1, 1904; 



II. Univ. Calif. Pub. Zool., 3, 1907. 



^ 



BOUGAINVILLIA. 



This form is not always obtainable during the summer 

 months. It occurs in fair abundance at Woods Hole earlier in 

 the season, attached to piles and floating timbers. 



1. Examine the colony for arrangement of branches, and 

 determine the relation of perisarc and ccenosarc. 



2. How do the hydranths differ from those of Obelia? Is 

 the number of tentacles constant? Is the hydranth as contrac- 

 tile as it is in Obelia? 



3. Look for gonosomes. The gonophores are borne singly 

 or in clusters on the main stem and branches. By examining 

 a number of buds the general method of medusa formation can 

 be determined. If possible, find (a) A young bud slightly 

 swollen showing the thin perisarc with the cellular layers inside 



3 



