larger jelly-fishes of our shores, which differ from the bell-shaped 

 hydroid medusae in their usually larger size and solid disk, as well 

 as in the larger number and greater complication of the water 

 tubes, which ramify and interbranch along the under side of the 

 disk; and in carrying their eggs in pouches. In our common 

 Aurelia Jlavidula There are four of these large pouches occupying 

 the centre of the disk. 



The life history of the Aurelia, which we will select as an ex- 

 ample of the mode of developmenUof this group, since it is best 

 known, is far less complicated than that of the Hydroids. The 

 ciliated planulae may be found in the egg pouches of the female 

 Aurelia during the last of summer. Soon Fig.63. 

 after the ectoderm and entoderm are 



ination of the ectoderm, as stated by Mets- 

 chnikoff, and they then pass into a gastrula 

 (planula) stage (Fig. 63, Gastrula of a 

 form allied to Aurelia ; a, moutli ; 6, gastro- 

 vascular cavity ; c, ectoderm ; d, entoderm ; Gastrula of an Aureiia-iike 

 after Metschnikoff) , with a mouth and Medusa, 

 long digestive cavity. After swimming about for a while they fix 

 themselves to some object at the bottom of the sea and soon a 



ire developed. When of this hydra-like form 

 >, older, after A. Agassiz) it is called a "Scy- 

 riginally, as well as the Strobila and Ephyra, 



