44 EMBEYOLOGICAL MONOGRAPHS. 



12-13. Abnormal Blastula: of IMothvria tuhiiln»i. From E. Seleiika, Zur Entwickelung der Holothurieu, 1876, 



ri. XIII. Quoted above. 



14-27. Homologies of EchiiwdcTm Larva:. From Jobaiiues llUller, Ueber den Allgemeinen Plan in der Entwicke- 

 lung der Ecbinodermen, Pt. VI., 1852, PI. II. Quoted above. 

 Anterior or oral jilastron. 



Posterior or anal plastron, iti which is placed o, the anal opening. 

 Intei-raediate oral area, in which is ijlaccd C, the mouth, and a, the anterior, i, the posterior edge of 



the transverse part of the oral ribratile cords ; c, the connecting vibratile cord between the oral 



and anal plastrons. 

 Posterior lobe of the vibratile cord of the oral i)lastron. 

 Anterior lobe of the vibratile cord of the anal plastron. 

 Arms of the anterior and posterior plastrons on the oral side. 

 Arms of the anterior and posterior part of the dorsal vibratili^ cord. 



Processes forming in Echini arms at the anal extremity, not in the line of the vibratile cord. 

 Connecteil vibratile cord of the dorso-anal system. 

 Conni^cted vibratile cord of the oral ventral plastron. 

 Brachiolarian appendages of the Starfish larva. The whole of the P.rachiolaria of fig. 27, beyond 



the braehiolarian arms, corresponds to the Starfish larval organ, such as has been figured by Sars, 



Thomson, Ludwig, and others. 



14-16. Shows the development of an Auricularia from the tj'pical Echinodermal larva, fig. 14. 



17-19. The development of an Ophiuran Pluteus from the typical Echinodermal larva, fig. 17. 



20-23. The development of an Echinoid Pluteus from the typical Echinodermal larva, fig. 20. 



24-27. The development of a Starfish Brachiolaria from the tyi>ical Echinodermal larva, fig. 24. 



For modifications of the typical form of development of the Holothurians, see PI. XIV. figs. 13-27, PI. XV. 



figs. 5-11. 

 For modifications of tlie typical form of development of the Opliiurans, see PI. III. figs. 1-20, 26-31. 

 For modifications of the typical form of development of the Starfishes, see PI. V. figs. 1-4, 15-49, PI. A'l. 

 For modifications of the typical form of develojuuent of the Sea-urchins, see PI. XII. figs. 30-34. 



