78 



SIR C. WTVILLE THOMSON ON CERTAIN ECniNODERMS. 



provisional mouth and no pseudembrj^ouic appendages whatever 

 are formed, and that the primary aperture of the gastrula re- 

 mains as the common mouth and excretory opening of the mature 



Ficr. 13. 



Ophiocoma dideJfhys, Wy. Thomson. Twice the natural size. 



form. From the appearance of the ovaries and of the broods of 

 young, I should think it probable that this species gives offyoung 

 in a continuous series for a considerable length of time, probably 

 for some months. 



I have selected for illustration in the foregoing pages, out of a 

 much larger number, eight examples representing four orders show- 



