MONOGRAPH OF THE EXISTING OBINOIDS. 359 



These have been described in much greater detail by Keichensperger. 



Reichensperger found these ceils only in gravid females, in the region where 

 the eggs are extruded from the pinnules. He was quite unable to find them in 

 males, and could detect only traces of them in unripe females. They do not appear 

 to occur in Isocrinus nor in any of the Comasterida;. 



The cement cells are almost exclusively confined to the ventral side of the 

 pinnules, occurring in a broad longitudinal band. In all probability they are 

 profoundly modified epithelial cells. 



As a rule they are elongate oval, on the average 0.012 mm. long by 0.004 mm. 

 in greatest breadth. The nucleus, whicli is small and often difficult to demonstrate, 

 lies near the base. 



The eggs of Antedon^ on coming to maturity, break through the piimule wall on 

 the ventral side ; after fertilization they are held fast to the outer side of the pinnule 

 until the ciliated larvae have developed. 



On both sides of the rents in the body epithelium through which the eggs are 

 extruded are numerous cement cells. As the eggs advance these cells empty almost 

 their entire contents on them, which, as a thick, half-solidified giunmy mass, clings 

 to the egg case, roughened by numerous minute spinelets, and fastens the egg to the 

 outer pinnule wall. About the eggs can be commonly seen long threads of the 

 hardened secretion. This secretion must be only very slightly soluble in water, or 

 it must entirely harden, for after the escape of the ciliated larva a part or even all 

 of the egg case often remains for a considerable time on the pinnules. 



GENITAL PORES OF THE MALE. 



Prof. William S. Marshall has described the genital pores of the male Antedon 

 mediterranea. While working with a series of sections of a male pinnule he noticed 

 a number of pores passing almost completely through the pinnule wall, which upon 

 further examination were found to be present in a niunber of pinnules on each arm 

 of the two specimens examined. As many as four pores were found on a single 

 pinnule, they having, however, no very definite position otlier than being in the 

 neighborhood of the sacculi. 



From the specimens studied lie was led to believe that these pores are present in 

 ripe pinnules, and that through them the spermatozoa are expelled. 



At these points the genital cord grows toward, and partially through, the wall 

 of the pinnule. The fully developed and developing spermatozoa show a longi- 

 tudinal linear arrangement, which is broken wherever one of the genital pores is 

 developed, and at this point they pass outward to fill the pore, undoubtedly re- 

 maining within it until its rupture, when they are expelled into the water. 



P. H. Carpenter has described the pores of the male in Pcecilometra acmla and 

 in Peinssometra angusticalyx. In these species the fertile part of the gonad is 

 short, thick, and rounded. It only extends over four or five of the enlarged and 

 broadened pinnule segments, and is protected by a tolerably regular pavement of 

 plates. At about the middle of its length one or two small conical projections rise 

 from it toward the ventral surface of the pinnule. Carpenter does not tliink that, 

 as a rule, there is more than one to each pinnule. 



142140— 21— Bull. S2 25 



