MONOGBAPH OF THE EXISTING CBINOIDS. 357 



B&ACHIAL AND PINNULE CISTS OF ANTEDON. 



Figs. 1305-130S, pi. 44. 



In 1885 P. H. Carpenter called attention to peculiar swellings which he very 

 frequently observed on the pinnules, and less commonly on the ai-ms, of Antedon. 

 From their appearance Carpenter thought that possibly they were caused by 

 myzostomes, and for that reason he sent a number of them to Prof. Ludwig von 

 Graff for examination. 



The latter foimd that the malformations of the pinnules are extraordinarily 

 numerous and occur on specimens of the several species of Antedon from the 

 most diverse localities. Sometimes they are hardly noticeable thickenings of a 

 single segment, or of two, less frequently of three, sometimes larger spherical 

 dilatations toward the adambulacral side. Somewhat rarely dilatations occur 

 which are really onty pits surrounded by a thickened wall. On the other hand, 

 there are not infrequently two or three such swellings on the same pinnule, and on 

 a single arm of an example of Antedon iifida from Milford von (irraff counted 

 7 of the malfonnations, and in all 14 characteristic swellings on one individual. 



The arm swellings are less numerous. On a specimen collected near (jibraltar 

 by the Vetfor Pisani three distinct deformities occur in close approximation. 

 The very slight swelling of the arm extends over two segments and is tolerably 

 uniform on either side. Von (Jraff observed, however, one-sided conical swellings 

 of the brachials, sometimes combined with an enlargement of the basal segment 

 of the attached pinnules. 



Von Graff opened 14 of these malformations under a lens, and. after decalcifi- 

 cation, cut longitudinal sections of them, but in no case did he find a myzostome or 

 any other encysted organism; instead, both in the various pinnule deformities and 

 in the arm swellings, he found a rounded brown foreign body which was appar- 

 ently the cause of the deformity, though he was not able to determine anything 

 definitely as to its nature or origin. 



The diameter of one of these spheres, from a pinnule swelling of an Antedon 

 bifida from Cumbrse, was 0.3 mm. Its substance was distinctly divisible into a 

 strongly refracting cortical layer and an opaque granular internal mass. The 

 former was radially divided into cell-like portions, and had quite the appearance 

 of cylinder epithelium both in optical section and on surface view; there was not, 

 however, any sharp boundary between the outer layer and the central mass. The 

 whole had thus the appearance of a superficially segmented ovum. 



These bodies sometimes lie in the center of the swollen segment in the cal- 

 careous substance, or near the integument, or even embedded in the latter. In 

 sections they are seen to be surrounded by a noncalcified tissue uniformly stained 

 by carmine. When the body lies just below the integument the tissue is con- 

 nected with the latter. 



The sections shed no light upon the nature of the included body. In a figure 

 given by von Graff of one of the spheres which had a diameter of 0.26 mm. the 

 cortical substance appears in part roughly divided, and in the central mass also 



