24 W. PEECY SLADEN. 



On the Homologies of the Primary Larval Plates 

 in the Test of Brachiate Echinoderms. 



By 



liV. Percy Sladen, F.Ii.S., F.G.S. 



With Plate I. 



All that had previously been written upon the subject of 

 homologous plates in larval Echinodermata was critically 

 discussed in the pages of this journal by my friend Mr. P. 

 Herbert Carpenter, in his able and philosophical memoir " On 

 the Oral and Apical Systems of Echinoderms/' i and in his 

 succeeding papers on Echinoderm Morphology .^ It will there- 

 fore be unnecessary for me to refer historically to the 

 conflicting views which have been held at different times by 

 those naturalists who have devoted their attention to the com- 

 parative embryology of the group, and who have endeavoured 

 to trace correspondent plates in the different orders. In 

 addition to systematising and consolidating what was known, 

 Carpenter has also extended our knowledge of the subject 

 greatly, not only by means of direct research but also by 

 furnishing an interpretation of observations made by others, 

 from which logical deductions had not previously been drawn. 

 As my friend's papers were written essentially from the 

 Crinoid standpoint, I propose in the present notes to approach 

 the subject from the Asterid side, because in the first place I 



1 Vol. xviii, 1878, p. 351, and vol. xix, 1879, p. 176. 



^ Vol. XX, 1880, p. 321; vol. xxi, 1881, p. 1G9; vol. xxii, 1882, p. 371. 



