ON THi; I MMIYOLOGY OF ECniNOPF.RMS. 



27 



EXPLANATION OF TIIK FIGU1M ^ 



With the exception of figs. 20, 30, and 84, which were copied from drawings made by Mr. Tappan, under 

 the direction of 1'rofessor Agassiz, the figures were drawn on wood by myself from the drawing* I made at 

 the time of this investigation. 



TOXOPNEUSTES DRORACHIENSIS A< . 



Fins. 1-28. 



The SJX nuns from figs. 1-18 inclusive* re all obtained fi m artificial fecundati* . 19-27 were 



caught with the dip-net ; fig. 28 was thrown up on the beach after a storm. 



EXPLANATION OF LETTERING. 



a, anus 



i, madreporic body. 



c, alimentary canal (intestine) 



cf, digestive cavity (stomach). 



e', «", e"' 



, e ,T , arms of the plutean form 



f, brachiolar arms ? 



g, tentacles round actinostome in Cuvieria. 

 g'y ambulacral tentacles of Cuvieria. 



4, teeth of young Echinus. 



/, body of larva of Cuvieria (pupa of M tiller) 



m, mouth. 



n, intojambulacral tubercles of Echinus. 



n', ambulacral tubercles. 



o, oesophagus. 



/?, pedi( tria. 



r. abactinal r ;ion. 



r* f main rod, formed first in the Echi 



r", r-»d of arm e". 



r'", hide [indent rod above ophagus. 



r ,T , anal point of junction of rods in the Ophiuran Pluteus. 



s, actinal region. 



s'j spots of arms e', e" of the Pluteus of Echinus. 



s", interambulacral spines of Echinus. 



*'", younger spines of Echinus. 



t, tentacles. 



t', odd terminal tentacle 



v, anal part of vibratile chord. 



t;', oral portion of vibratile chord. 



Pluteus 



r", vibratile epaulettes. 



w, water-tube. 



tr', water-tube leading to madreporic body 



y, terminal arm-plate of Ophiuran. 



y', !e arm-plates of Ophiuran. 



In fig. Sir -hould ! v\ and vice versa. 



For the earlier stages compare figs. 1 -5 of Proc. Am. Acad., from which the earlier stages of the Echinus 

 Pluteus do not differ greatly. 



Fig. 1. Profile view of an Echinus Pluteus eighty-eight hours after artificial fecundation. 

 Fig. 2. The same as fig. 1 , seen from above. 



Fig. 3. Profile view of a plutean form >mewhat more advanced than in fig. 1 ; the digestive cavity, tf, is 

 bent very considerably towards the actinal side. 



Fig. 4. View from above of a Pluteus in which the digestive cavity, d 9 is somewhat differentiate 1 by con- 



