the- Asterid, Crinoid and Ophiurid groups, which nay 

 have a bearing upon the subject, and in the same con- 

 nection,! rich to call attention to how well McBRIDES 

 hypothetical ancestor or the Asterids and Crinoids, 

 ( 9. Fig. . ) .when details are not too closely com- 

 pared ,fits into the facta of the larvs of O.brevi- 

 opina . 



In one of the Asterids ,GOTO has shorn that 

 toward the end of metamorphosis the alnost complete 

 star sits as a cap at the posterior end of the larva 

 with its aboral end posterior , its oral surface an- 

 terior , the trivium ventral and the bivium dorsal. 



In Antedon f liKe the star-f ish,the rotation ' 

 brings the developing crinoid head to the posterior 

 end of the larva ;but differing diametrically from 

 the star-fish, in that the oral instead of the aboral 

 surface of the crinoid is posterior, but this diffor- 

 ence does not in any affect the homologies between 

 the two groups as has been supposed. 



In Ophiurs brevispina th: relation of larva and 

 adult at the tir.« of metamorphosis is approximately 

 the earn: as ie shown in stage F,in which ventral in 

 the larva is ventral (oral) in the adult. 



Now if we talis the ophiuran larva at star;: F 

 and imagine the disk to rotate in such a way as to 



