MUSEUM OF COMPAKATIVE ZOOLOGY. 149 



TV). Right water- vessel, hydrocoel. 



sp. Spine of ami. 



spl. Spoon-shaped plate. 



t. Teeth. 



tf. Unpaired or terminal feeler. See wt. 



to. Torus angularis, jaw-plate. 



tp. Terminal plate, terminal. 



u. Connection of pentagonal larva with parent. In stages earlier than 



pentagonal larva also found. 



V. Ventral plate, lower arm-plate. 



wt. Terminal end of water- vessel of the arm. 



PLATE L 



Figures drawn with Camera lucida, Obj. BB. 



Fig. 1. Pluteus of OphiophoUs aculeata, Gray, in a little older condition than that 

 figured in Fig. 23, PI. L, Bull. Mus. Comp. ZooL, Vol. XIL No. 4. 

 " 2. The same somewhat older. Seen from side on which mouth opens. 

 " 3. Adult pluteus of 0. aculeata before young Ophiuran has begun to form. 



The drawings from which these figures were made are from plutei taken at Frye's 

 Island, New Brunswick. This island bears the name of CailifiTs Island on the Admi- 

 ralty Chart. 



The same plutei are common at Eastport, Maine. 



PLATE II. 

 Figures drawn with Cainera, Objs. BB, DD, Zeiss. All except Fig. 1 with Obj. BB. 



Fig. 1. Blastosphere of ^mp^mra sg-wamate. Diameter, .15 mm. 

 " 2. Same, younger. 

 " 3. Gastrula. 



" 4. Ventral view of a bisymmetrical larva, unattached. 

 " 5. The same, lateral view, attached. 

 " 6. Somewhat older larva than tlip last, showing +he vasoperitoneal sacs or 



water-tubes. 

 " 7. The last, lateral view, unattached. The remnant of the attachment in the 



upper right-hand comer. 

 " 8. An older larva than the last, attached. Dorsal view. 

 " 9. The same, older. 

 "10. The same, still older. 

 "11. Somewhat older larva. 

 "12. A pentagonal attached larva with well-formed radial, dorsocentral, and 



terminal plates. Abactinal view. Attachment at u. 

 "13. Youngest free Amphiura, unattached to parent. Found free in mother. 



Abactinal view. The great prominence of two of the terminal plates, tp, 



is due to the position which the specimen had when drawn. 



