214 PROCEEDINGS OP THE ACADEMY OP [1884. 



portions of those cells which seemed to be least matured were 

 longer than those of their older neighbors, subclavate or spindle- 

 shaped and rounded at the extremities. The otliers are cylin- 

 drical or slightly widening downwai'ds and shorter tlian the 

 former bj^ the invagination of the terminal portion of the 

 ectocyst. This has the effect of producing the angular appear- 

 ance of the orifice, so familiar in the older species ; but while 

 that is generally quadrangular, this has frequently five or more 

 sides. The younger cells are nearly transparent, but they darken 

 with age and become somewhat encrusted with adherent particles 

 and overgrown by commensal parasites, Limnias, Pi/xicola, and 

 the like. 



The polypides are shy, but fond of the light, and when other- 

 wise undisturbed will remain for a long time protruded in the 

 full glare of microscopic illumination. It can then be seen 

 that the lophophore is circular, without epistome, supporting 

 ordinarily twenty tentacles, taking the shape of a claret glass and 

 opening upwards. (Nineteen and twenty-one tentacles have 

 been doubtfully counted, while the above-mentioned number is 

 frequent; F. Ehrenbergiis universally stated to have but sixteen). 

 A peculiarity of the tentacles is the presence upon the outer 

 median line of each, of a ratlier sparsely filled series of quiescent 

 setae, in strong contrast with the rapidly moving cilia around 

 them. 



The development of this polyp from the ovum, of which 

 interesting hints have been obtained, and its internal structural 

 peculiarities, are reserved for further study, and if satisfactory 

 results shall have been attained, they will be treated of in a later 

 paper. The nearly simultaneous observation of this species in 

 three distinct localities, and its abundance in each, indicates that 

 it is probably not uncommon, and excites surprise that it does 

 not appear to have been previously noticed. 



August 12. 

 Mr. Thomas Meehan, Vice-President, in the chair. 

 Fifteen persons present. 



A Large Zircon. — Dr. A. E. Foote recorded the discovery of 

 the largest crystal of zircon ever known. It is dj inches high, 

 4 inches on one face and 3| inches on the other. It undoubtedly 

 originally weighed twelve pounds, but owing to a small portion 

 being lost by fracturing it now weighs but eleven and three-quarter 

 pounds. The largest cr3^stal ever known before weighed less 

 than three pounds. The crystal is doubly terminated, and, 

 though somewhat broken in taking out nearly all the pieces were 

 saved. At one end there are two terminations and one of these 



