Marvels of Pond- Life. 113 



lateral appendages of the Annelida, necessitates tlieir 

 assemblage with the Arthropoda in one great division, 

 or sub-kingdom, of Annulosa. 



Tracing analogies between the Echinoderrnata (sea 

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

 worms), he places them together as Annii/oida. 



Cephalopoda, Pteropoda, Pul mo-gasteropoda, and 

 Branch io-gasteropoda, having resemblances of nervous 

 system, and '^ all possessing that remarkable buccal 

 apparatus, the Odontophore,'' are placed together by 

 him asOnoNTOPHORA. TheOdontophores (tooth-bearers) 

 are familiar to microseopists as the so-called palates of 

 mollusca. Placing with the above the lamelliljranchial 

 mollusks (moUusks with gills formed of lanielhe or 

 little plates), Aseidioida (ascidians), 15rachiopoda (lamp- 

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

 forms another great group, Annuloida. 



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

 (polyps) constitute the Cq:lentera of Frey and Leuekart. 

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

 substance of the body is differentiated into those histo- 

 loerical elements which have been termed cells, and the 

 latter are previously disposed in two layers, one external 

 and one internal, constituting the ectoderm and cndo- 

 derm. Among animals which possess this histological 

 structure the Coclenterata stand alone in havin*,' 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 C'tenophora 

 should prove a partial exception to the rule) are i)rovidcd 

 with very remarkable organs of oflencc or defence, 



