SERTULARIA GONIONEMUS. 29 



ruptures and liberates the eggs into the sub-umbrellar cavity. 

 Cleavage stages are frequently found, and planulce, the lar- 

 val stage that is finally set free, may be found. In old gono- 

 somes, where most of the gonophores have matured their 

 sexual products and the outer end of the blastostyle has broken 

 down, especially large planulse may frequently be found. 

 These may be liberated with needles and studied with a high 

 power for cilia and the arrangement of cells. Older planulse 

 will show a streak that indicates the formation of a cavity inside. 



Planulse of this kind placed in a watch-glass of sea-water 

 and covered to prevent evaporation will soon attach and 

 develop into hydranths. When attached the sea-water should 

 be changed twice a day. Without feeding development is not 

 continued far. 



Make drawings of gpnosomes and of a planula. 



SERTULARIA. 



In habits and relation of parts there is nothing fundamentally 

 different from the other forms studied. The gonosomes present 

 another modification. 



1. The male gonosome has the blastostyle pressed to one 

 side and carries a single gonophore with prominent manubrium 

 and a mass of sperm. The sperm are actually between the 

 ectoderm and endoderm of the manubrium. 



2. The female gonosome has the blastostyle pressed to one 

 side and from it originate one at a time vestigial gonophores 

 that in turn push toward the distal end of the gonangium and 

 discharge their eggs into a specially constructed brood pouch, 

 the acrocyst. By opening acrocysts with needles stages in 

 development up to planulse may be obtained. 



Make a drawing showing a female gonosome with an acrocyst. 



GONIONEMUS. 



The complete life-history of this form is not known, but 

 from its structure we are led to believe that it belongs to the 

 suborder Leptomedusse. It is found in considerable numbers 



