12 EMBRYOLOGICAL MONOGRAPHS. 
13. Incipient rosette formed by the coalescence of the five altered basals in a young Antedon. 
14. Skeleton of base of calyx of young Antedon, seen from its internal or ventral side ; showing the five basals (d) 
altered by endogenous growth in preparation for the formation of the rosette. 
15, Skeleton of base of calyx of young Antedon seen from its dorsal aspect, the centrodorsal plate haying been 
removed ; showing that the central space round }, 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 calyx, by the secondary 
endogenous growth, with the same system of axial 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 4, 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 ; <-a—> 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 the rudimentary type, the radial and brachial plates, and the extension of the visceral disk as far 
as the third radial. 
18-21. Comatula rosacea, continued. From George J. Allman, On a Prebrachial Stage in the Development of Co- 
matula and its Importance in Relation to certain Aberrant Forms of Extinct Crinoids (1863), Pl. 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. The 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 The same with the cirri entirely withdrawn, and the roof-plates closed. 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 primiiren Steinkanal der Crinoiden, nebst vergleichenden 
anatomischen Bemerkungen iiber die Echinodermen iiberhaupt, 1880, Pl. XII. Zeits. f. Wiss. Zool., 
XXXIV. Morphol. Studien an Echinodermen, II. Heft 1. 
22. Optical longitudinal section of an Antedon larva. M, mouth; p/, cesophagus; D/’, stomach ; LL’, body cav- 
ity ; H, position of the so-called heart ; w, water-system ring ; s7, stone canal; 7, 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 ; 1, 1’, T//, tentacles ; 
other letters as in fig. 22. 
