Invertebrate Gallery of the Indian Museum. 17 



spicules cemented together by a substance known as 

 " spongin " chemically very similar to horn, or is formed 

 entirely of spongin fibres without any spicules whatever. 

 The common bath-sponge is a familiar example of this last 

 group. In Halme the horny skeleton is strengthened with 

 grains of sand. The Cornacuspongix are represented in 

 the collection by the following genera : — Esperella, fo- 

 trocha, Clathria, Echinonetna^ Plumohalichondria^ Clath- 

 rtssa, Thalassodendron, Echinodictyum, Caulospongia ; 

 Reniera, Haplochalina, C/ialinissa, Chalina, Tuba ; 

 Phyllospongia, Chalinopsilla, Hippospongia, Halme, Stel- 

 osf)otigia, Hircinia, Cacospongia, Carterispongia, and 

 Dendrilla. 



PHYLUM II OF THE COELENTERATA. 



CNIDARIA (STINGING ZOOPHYTES). 



[Cases 3—16], 



The other great group of the Coelenterata is that of the 

 Cnidarta, or Stinging Zoophytes, distinguished from the 

 Porifera or Sponges in possessing for the ingestion of food 

 a mouth surrounded by tentacles, instead of pores, in 

 being provided with special stinging-cells for defence and 

 for disabling their prey, and in being possessed of a true 

 stomach, as well as of the elements of a muscular and 

 nervous system. 



There are two great divisions of the Cm'daria, namely, 

 (i) the division typified by Hydra, in which the mouth is a 

 simple orifice in the body-wall, and leads directly into the 

 stomach ; and (2) the division typified by the Sea-anemone, 

 in which the mouth is formed at an invagination of the 

 body-wall, the invagination forming an ectodermal gullet. 

 Of these two divisions the first consists of the one Class 

 Hydrotnedusse, and the second consists of three Classes 

 the Ant ho 20a, the Scyphomedusse, and the Ctenophora, 



B 



