BROOKS AND RITTENHOUSE: ON TURRITOPSIS. 437 



CALLITIAKA: Tentacles numerous, in two alternating rows, one 

 row without ocelli, and the other with two ocelli on each tentacular 

 bulb; lips simple; gonads slightly split in perradii; proximal regions 

 of radiating canals with chorda-like endodermal cells. 



MCCRADIA gen. nov. (Modeeria in part). Tentacles numerous, in 

 one row, with a single ocellus on velar side of each tentacular bulb; 

 oral lips branched once dichotomously, perradial gonads slightly split 

 in perradii; proximal regions of radial canals with chorda-like endo- 

 derm. 



PART 3. EMBRYOLOGY OF Turritopsis nntricula. 



BY SAMUEL RITTENHOUSE 



INTRODUCTION. 



Work on the embryology of Turritopsis nntricula was begun at the 

 suggestion of Professor Brooks. The material was collected and the 



~~ 



observations on the living specimens were made during the summers 

 of 1903 and 1904, while I occupied a table at the United States fish- 

 eries laboratory at Beaufort, North Carolina. Turritopsis is one of 

 the most common medusae in the harbor during the summer. In the 

 two years that I was there they became abundant in the beginning of 

 July and remained more or less plentiful until I left Beaufort Septem- 

 ber 13th. While the medusae could be collected in fairly large num- 

 bers, many of them were immature. They lay only a limited number 

 of eggs. Material was preserved and sectioned, however, for the 

 study of such facts as could not be made out from the living forms. 

 The work was finished in the Biological laboratory of the Johns 

 Hopkins university. 



DEVELOPMENT OP THE OVARIAN EGG. 



The ova develop in the ectodermal layer of the manubrium. The 

 epithelium becomes very much thickened in four regions; these en- 

 larged areas form the ovaries. The primitive ovarian cells when first 

 differentiated are larger than the ectodermal cells of other parts. 

 Their protoplasm becomes homogeneous and of a finely granular 

 character. The nuclei are less hyaline in appearance; and the 



