254 



life. 2^Vi- The line seen across the ventral transverse rods is the lower limit of 

 the suboral cavity. 

 Fig. 6. Young larva of Astropyga pulvinata (Lamk.), 5 days old; ventral view. Drawn 

 from life. "o/^. 

 7. Larva taken pelagically, probably belonging to Astropyga pulvinata. Seen in some- 

 what oblique side view. Some dislocation has occurred; the anal area is somewhat 

 twisted to the left so that the side area of the larva has become too broad. The 

 figure is slightly corrected, the postoral (p. o.) and posterodorsal (p. d.) arms being 

 in a more upright (but unnatural) position in the specimen from which the figure 

 has been drawn. The basal part of the left postoral rod not to be seen quite di- 

 stinctly, that of the posterodorsal rod quite indistinct in the specimen. ^*7i- P- tr. 

 posterior transverse rod. 



Plate VI. 



Fig. 1. Larva of Arbaciid; taken pelagically off the Azores. The postoral and posterodorsal 

 arms broken; their length must considerably surpass that shown in the figure. ''%• 



2. The same larva, more magnified (°°/i). The larva is in beginning metamorphosis, 

 the anterolateral and preoral arms are not broken. The large fenestrated plate 

 at the base of the postoral (and, less developed, the posterodorsal) rods is not cha- 

 racteristic of the larval skeleton but is connected with the metamorphosis, p. 

 pedicellaria; p. tr. posterior transverse rod. 



3. Larva of Hetiocidaris tuberculata (Lamk.), seen from the posterior end; showing 

 the position of the ventral (v. tr.) and dorsal transverse rods (d. tr.); p. tr. posterior 

 transverse rod; da. dorsal arch; p. o. postoral, p. d. posterodorsal arm; p. 1. postero- 

 lateral lobe. 225/^ 



4. Larva of Temnotrema sculpta A. Ag., 20 days old. Drawn from life; ventral view. 

 The skeleton was merely sketched in the original drawing; as it has been dissolved 

 in the preparation, so that the sketch could not be completed, it had to be omitted 

 in the figure, ^""/i- 



5 — 6. Young larvse of Holothuria n. sp. (?), from the ventral side. Fig. 5 represents 

 a specimen 3 days old, Fig. 6 another, 8 days. old. The rectum is indiscernible. 

 The frontal area in fig. 6 probably too narrow, due to contraction on preserv- 

 ation. 18»/i. 



Plate VII. 



Fig. 1. Larva of Mespilia globulus (Linn.), 15 days old; seen from above, but in such a 

 position that the body is leaning somewhat over to the ventral side. The fact that 

 the posterodorsal arms are narrower than the postoral arms in this figure is due 

 only to the oblique position; in reaUty these four arms are of the same width. Drawn 

 from life. "»/i. 



2. Larva of same species, ventral view; drawn from a preserved specimen. (This ac- 

 counts for the narrowness of the postoral and posterodorsal arms as compared 

 with fig. 1.) Beginning metamorphosis; two pedicellariai have appeared in the 

 posterior end. Same age as the larva represented in fig. 1. i»»/i. 



3. Larva of Arbacia stellata (Blv.); dorsal view. 'Vi- 



4. Young larva of Lytechinm panamensis Mrtsn., ventral view; 5 days old. Drawn 

 from life, ^^o^^ 



5. Young larva of Lytechiims anamesus H. L. Clark; side view; 7 days old Drawn 

 from life. '%. 



Fig. 1. 

 2. 

 3. 



Plate VIII. 



Young larva of Lytechinus variegatus (Lamk.), 2 days old. Ventral view. Drawn 

 from life. "'/i. 



Young larva of Tripneustes esculentus (Leske), 3 days old. Ventral view. Drawn 

 from life, ^oo/^ 



Larva of Lytechinus anamesus H. L. Clark, 7 days old. Not yet fully formed. Ven- 

 tral view. Drawn from life. ""/j. 

 4. Larva of same species, same age as fig. 3; dorsal view, Drawn from life. »»/,. 



