52 COELENTERATA 



the ectoderm of the subumbrella so that this space is practi- 

 cally obliterated. These sperm become active when liberated 

 in sea water. 



6. The female gonophore when mature is more elongated, 

 shows indications of tentacles at the free extremity, and there 

 is an actual subumbrellar space. The eggs are formed in 

 the ectoderm of the manubrium and are shed into the sub- 

 umbrellar cavity. An egg develops into a larva called an 

 actinula. With needles open a female gonophore and ex- 

 amine the developmental stages. These are: (a) somewhat 

 irregular disk-shaped embryos with a variable number of pro- 

 jections (the forming tentacles) around the margin, (b) 

 Older stages with the tentacles more developed and with disk- 

 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. 



Actinulae kept in a covered watch glass of sea water will 

 attach and form the basis of new colonies. 



Make drawings of gonosomes, gonangia, and developmen- 

 tal 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 hydranth is evident. 



Hargitt: The Early Development of Pennaria tiarella. Arch. f. Ent- 



wicklungsmech., 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. 



BOUGAINVTLLIA 



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. 



