12 EMBr.YOLOGICAL ilOXOGlJAPHS. 



13. Iiii-iiiimit rosette formed by the coalesceiu-e of tlie five altered basals in a young Antedon. 

 1-t. Skeleton of base of calyx of young Antedon, seen from its internal or ventral side ; showing the five basals (i) 

 altered by endogenous growth in [ireiiaration for the formation of the rosette. 



15. Skeleton of base of ealy.x of young Antedon seen from its dorsal aspect, the centi'odorsal plate having been 



removed ; showing that the central space round b, on the under side, has been enlarged by the resorption 

 of a part of the original basals, though it is still contracted, near the cavity of the cah-.x, by the secondary 

 endogenous growth, with the same system of a.vial canals as are figured in the subsequent figure (fig. 16). 



16. The same as fig. 15, seen from the ventral aspect ; showing the five basals grouped around J, and traversed 



by canals for the radiating cords of the sarcodic axis, of which a trunk enters each basal from the central 

 space, and then subdivides into two branches, that pass into the two radials between which the salient 

 angle of the basal projects ; thus each first radial receives cords from two basals, and these are lodged in 

 two canals which coalesce into one towards its distal border, each of them having first become connected by 

 a lateral branch with the like canal in its contiguous first radial ; <— «— > shows the position of the anal. 



17. Calyx of young Antedon just detached, seen from its dorsal side, showing five cirri of the mature type and 



five of tlie rudimentaiy type, the radial and brachial plates, and the extension of the visceral disk as far 

 as the third radial. 



18-21. Comalala rosacea, conWnwii.. From George J. AUman, On a Prebrachial Stage in the Development of Co- 

 matula and its Importance in Relation to certain Aberrant Forms of Extinct Crinoids (1863), PI. 13. 

 Trans. R. S. Edinburgh, XXIII. Part II., 1864. 



18. The animal with its roof-plates fully expanded and the cirri extended from between their edges. 



19. Tlie same in the act of expansion. 



20. The same with the cirri entirely withdrawn, and the roof-plates closed. 



21. Outline of the body looking down upon it from the vertex. 



22. 23. Antedon Larva. From H. Ludwig, Ueber den primaren Steinkanal der Crinoiden, nebst vergleichenden 



anatomischen Bemerkungen iiber die Echinodermen iibcrhaupt, 1880, Pi. XII. Zeits. f. Wiss. Zool., 

 XXXIV. Morpliol. .Studien an Echinodermen, II. Heft 1. 



22. Optical longitudinal section of an Antedon larva, nr, mouth ; d', cesophagus ; d", stomach ; L l', body cav- 



ity ; II, position of the so-called heart ; w, water-system ring ; s T, stone canal ; t, tentacle ; K, reddish- 

 brown body ; F, axial cord of the stem. 



23. Diagrammatic sketch of an Antedon larva, d'", intestine ; A, anus ; P, pore in calyx ; T, t', t", tentacles ; 



other letters as in fig. 22. 



