ANTHOMEDUSiE TUBRITOPSI8. 



145 



As in MetschnikofF's <>,,,iin<i /inntitn and Margin's embryos ol ' Pi-iiiinrin, this ii regularly 

 shaped morula gradually changes into an oval embryo, the surface of which becomes ciliated. BO 

 that it swims upward from the bottom. This takes place at about 4 in the afternoon in eni^ 

 which were laid between 5 and 6 in the morning. 



Rittenhouse finds that during this period, when the loose, irregularly shaped mass of cells 

 shapes itself into an oval embryo, the ectoderm and entoderm are formed. During this period 

 "the cell-boundaries are lost tor a short time and a syncvtium is formed. This syncytial 

 structure is crowded with yolk-granules and nuclei are scattered throughout the protoplasm. 

 The nuclei soon become more numerous near the periphery and the cell-walls begin to appear" 



I'll.. 7'i. - Tun l,Vy/iM< tint! i< Illtl, ,lttrr Hri'oks, in Mi'tll. linstnn Sm . N.ll. Hrl. HvJroul .llhi \nnnr ii"i!v^.l. 



between the peripheral nuclei. These peripheral cells are to become the ectoderm, which is 

 soon separated from the inner, structureless mass by the development of the meaoglcea. I his 

 inner mass afterwards acquires cell-boundaries between its nuclei, and still later a central 

 cavity, the ccelenteric space, develops; and thus the entoderm is formed. This ccelenteric 

 cavity does not develop, however, until the larva is 48 to 60 hours old. The s\ IH\ tmm con- 

 dition in Turritopsil is much more complete than is seen according to Hargitt in Pennaria, 01 

 in Bougainvillia, according to Gerd, 1892. 



