XII. — CRUSTACEA AND LOWER INVERTEBRATA. 103 



part of the spicules covered by a species of Polythoa, an Alcyon- 

 arian coral, which lives as a commensal with the sponge. Another 

 important and rare species from the " Porcupine " expedition is 

 the Holtenia Carpenteri. 



The OeratOSpongia, or Horny Sponges, to which the 

 common " Toilet Sponge " belongs, are largely represented. 

 Amongst those on exhibit are some varieties of the commercial 

 sponge found on the Australian coast. 



Sub-Kingdom VI. -PROTOZOA. 



This sub-kingdom consists of animals of small size, extremely 

 simple, and destitute of any definite cell-tissues. It includes all 

 the lower forms of animal life, such as Infusoria, Gregarina, 

 Amoeba, Radiolaria, and Foraminifera. 



The Foraminifera is the only group at present represented 

 in the Collection. The bodies of animals in this group consist of 

 jelly-like masses, or sarcode. They are capable of throwing out 

 from the mouth, or through perforations scattered over the surface 

 of the shell or test, long foot-like processes, called pseudopoda or 

 " false feet." The shells of these animals are usually composed of 

 carbonate of lime or of sand grains cemented together, and they 

 may be either single or many chambered. This sub-kingdom is 

 represented in the cases by a series of specimens from Port 

 Jackson as well as by a set of greatly enlarged models. Some of 

 the specimens may be compared with the models, as for instance 

 Peneroplis planatus, which will give some idea of the relative size 

 of the species. (See Case 1.) 



