336 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



This was the natural consequence of the change of function of 

 the water-pores and the Coel enteric apparatus, — the ciliated 

 chambers with their cilia-motion introducing nourishing material 

 took the place of apprehensive tentacles, and with the latter the 

 Cuidoblasts vanished, and the easier, the less the Sponges needed 

 further protection in consequence of their extremely well developed 

 skeleton, which also often contains very sharp spicules which are 

 perfectly analogous to Cnidoblasts (for instance, the superficial 

 floricome spicules of Euplectella (1). Sponges, which besides this 

 often smell very badly, don't appear to have many enemies. In 

 fact they seem not to be edible by other animals, which we may 

 also conclude from the frightening colours (yellow, orange, 

 vermillion, &c.,) of the sponges which grow in shallow water. 

 Also, the animals which so often live in the cavities of the Sponges 

 are, with the exception of a few minute parasitic algse, not 

 parasites, but only commensals, which find shelter in the detested 

 Sponges. 



It is, of course, possible that the Sponges branched off at a very 

 early stage from the stem of the Coelenterata, when tbey possessed 

 neither tentacles nor Cnidoblasts. 



Of much importance in this question the fact appears, that 

 a radial structure is just as much exception in the Sponges as it is 

 the rule in the higher Coelenterata : both probably had bilateral 

 symmetrical ancestors, out of which, perhaps in correlation with 

 the tentacles, the higher Coelenterata were developed as radial 

 animals (] the Author). 



This structure is also sometimes met with in young sponges 

 (compare the Protactinia-stage of Reniera), and sometimes also in 

 the adult. 



The following may be the points of coincidence between Sponges 

 and the higher Coelenterata (2). 



(1) F. E. Schulze. On the Structure and Arrangement of the soft parts 

 in Euplectella aspergillum. Voyage of H.M.S. Challenger. Sponges 

 Hexactin, pi. A, tigs. 3, 4, 5. (Proc. Phil. Soc, Edinburgh, 1879, the 

 Author.) 



(2) This comparison, of course, is carried out with an ideal form which 

 has been constructed out of the single peculiarities of different Cuolenterata, 

 which are nothing else but different modifications of the same type. 



