Marvels of Pond- Life. 143 



lateral appendages of the Annelida, necessitates their 

 assemblage with the Arthropoda in one great division, 

 or sub-kingdom, of Annulosa. 



Tracing analogies between the Echinodermata (sea 

 urchins, star-fish, &c.) and the Scolecida (intestinal 

 worms), he places them together as Annuloida. 



Cephalopoda, Pteropoda, Pulmo-gasteropoda, and 

 Branch io-gasteropoda, having resemblances of nervous 

 system, and " all possessing that remarkable buccal 

 apparatus, the Odontophore," are placed together by 

 him asODONTOPHORA. TheOdontophores (tooth-bearers) 

 are familiar to microscopists as the so-called palates of 

 mollusca. Placing with the above the lamellibranchial 

 mollusks (mollusks with gills formed of lamellae or 

 little plates), Ascidioida (ascidians), Brachiopoda (lamp- 

 sheds), and Polyzoa, in spite of their differences, he 

 forms another great group, Annuloida. 



The Actinozoa (anemonies, &c.) and the Hydrozoa 

 (polyps) constitute the Coilentera of Frey and Leuckart. 

 " In all these animals," says Professor Huxley, " the 

 substance of the body is differentiated into those histo- 

 logical elements which have been termed cells, and the 

 latter are previously disposed in two layers, one external 

 and one internal, constituting the ectoderm and endo- 

 derm. Among animals which possess this histological 

 structure the Coelenterata stand alone in having an 

 alimentary canal, which is open at its inner end and 

 communicates freely by this aperture with the general 

 cavity of the body/'' and " all (unless the Ctenophora 

 should prove a partial exception to the rule) are provided 

 with very remarkable organs of offence or defence, 



