30 EMBRYOLOGICAL MONOGRAPHS. 
41. Arbacia punctulata. From Alexander Agassiz, Revision of the Echini, Part IV., 1874, p. 729, fig. 66. 
Illust. Cat. Mus. Comp. Zool., No, VII., Pt. 1V. 
Adult Pluteus of Arbacia punctulata; m, mouth. The dark spots of the anal extremity are the pigment spots 
of the young Arbacia. 
42-43. Arbacia punctulata. From H. Garman and B. P. Colton, Some Notes on the Development of Arbacia 
punctulata, Lam., 1882. Johns Hopkins University, Baltimore, Studies from the Biologieal Laboratory, 
IT.; No: 2,,Pl. XVI 
42. Young Arbacia which has begun the resorption of the Pluteus; the oral part of the Pluteus is greatly 
shrunken (0 /). 
43. The process of resorption is more advanced, only a trace of the oral part of the Pluteus is left (07), and the 
limestone rods of the anal arms appear like tall spines on the abactinal side of the yonng Arbacia. The odd 
tentacular suckers are very prominent. 
44, 45. Arbacia punctulata. From Alexander Agassiz, Revision of the Echini, Pt. IV., 1874, p. 734, figs. 68, 69. 
Illust. Cat. Mus. Comp. Zool., No. VII. Pt. IV. 
44, Young Arbacia punctulata, 1.5mm, in diameter, including the spines, seen from the abactinal side, showing the 
anal system with its four plates. The apical system covers nearly the whole abactinal area, and is covered 
by embryonic sessile tubercles : a few pedicellarie 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 ambu- 
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 are 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 the actinal sur- 
face covering the ambulacral tubes ; the longest tentacles are those nearest the odd terminal tentacle; the 
odd tentacle is a small, short, slender tube without a sucking disk. 
