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THE CANADIAN NATURALIST. 



[June 



orifices. The sixth he supposes to be both mouth and vent, 

 which accords with my view. (Mon. der Blastoideen, p. 378). 

 In 1868 I discovered the five small pores at the apical extremities 

 of the ambulacral grooves. (This Jour., II, xcvii, p. 353, and 

 Annals Nat. Hist., IV, vol. 4, p. 76). In general it is difiicult 

 to to see these pores, but if a silicified specimen, tvhich has been 

 fossilized in a calcareous matrix, be placed in an acid for two or 

 three minutes, the acid cleans them out and they then become 

 distinctly visible. I believe these to be the pores through which 

 the ovarian tubes passed outward along the grooves to the pinnulae. 

 There are thus, sixteen apertures in the apex oi' Niideocrimis, — 

 ten spiracles, five ovarian orifices, and one oro-anal aperture. 

 There are no true radial plates. The whole of the test with the 

 exception, perhaps, of the ambulacra belongs to the perisomatic 

 system, 



8. On the occurrence of Embryonic forms among the 



Paleozoic Echinoderms. 



8. 



9, 



10. 



11. 



TTlV 



Fig. 8. Bipinnaria asterigeraSsiVS, (copied from 

 Muller). a, the stomach; b, part of the body of 

 the larva; c, ambulacral centre, position of the 

 permanent mouth, in this stage not open ; d, one 

 of the five ambulacral canals; e, sand canal; /, 

 madreporic plate ; ?», entrance into the stomach ; 

 o, oesophagus ; j:>, larval mouth or pseudostome ; 

 y, oesophageal ring; v, vent. 9. Ideal figure de- 

 scribed below. 10. Codonites stelliformis, ohlique 

 view to show both body and summit. 11. Summit 

 of fig. 10. 



No proposition in Natural History has been more clearly 

 demonstrated than this : — That, in general, the paleozoic animals 



