30 EMBRYOLOGICAL MONOGItAPIIS. 



41. Arbacia punctxdata. From Alexander Agassiz, Revision of the Echini, Part IV., 1874, p. 729, fig. 6ij. 



lUust. Cat. Mus. Conip. Zool., No. VII., Pt. IV. 



41. Adult Pluteu.s of Arbacia pimctulata; m, mouth. The dark spots of the anal extremity are the pigment spots 



of the young Arbacia. 



42-43. Arbacia jmnclulata. From H. Garman and B. P. Colton, Some Notes on the Development of Arbacia 

 puuctulata. Lam., 1882. Johns Hopkins University, Baltimore, Studies from the Biological Laboratory, 

 II., No. 2, PI. XVIll. 



42. Young Arbacia wliicli lias begun the resorption of the Pluteus ; the oral part of the Pluteus is greatly 



.shrunken (o /). 



43. The process of resorption is more advanced, only a trace of the oral ])art of the Pluteus is left (o /), and the 



limestone rods of tlie anal arms a[>pcar like tall spines on the abactiual side of the yonng Arbacia. The odd 

 tentacular suckers are very prominent. 



44. 45. Arbacia punctii/ala. From Alexander Agassiz, Revision of the Echini, Pt. IV., 1874, p. 734, figs. 68, 69. 



Illust. Cat. Mus. Comp. Zobl., No. VII. Pt. IV. 



44. Yonng Arbacia punctidata, 1.5 mm. in diameter, including the spines, seen from the abactiual side, showing the 



anal sj'stein with its four plates. The apical system covers nearly the whole abactinal area, and is covered 

 by embryonic sessile tubercles : a few pedicellariie have made their appearance. The edge of the test carries 

 huge flattened spines triangular in section, nearly equalling in length the diameter of the test. The amtu- 

 lacral suckers are slender, .some of them longer than the diameter of the test, and provided with somewhat 

 pointed sucking disks. The whole test and the spines ai-e thickly covered with dark violet pigment .spots 

 and patches. 



45. The same as fig. 44, .seen from the actinal side, showing the connected limestone deposit of tlie actinal sur- 



face covering tlie aniliulacral tubes ; the longest tentacles are those nearest the odd terminal tentacle ; the 

 odd tentacle is a small, short, slender tube without a sucking disk. 



