THE MORPHOLOGICAL COMPOSITION OF ANIMALS. 81 



among them, are shown in Fig. 141. And setting out from 

 these, we may ascend in various directions to kinds com- 

 pounded to an immense variety of degrees in an immense 

 variety of ways. In all of them, however, the separability of 

 the major individuality into minor individualities, is very in- 

 complete. The portion of sarcode contained in one of these 

 calcareous chambers, gives origin to an external bud ; and 

 this presently becomes covered, like its parent, with calcareous 

 matter : the position in which each successive chamber is so 

 produced, determining the form of the compound shell. But 

 the portions of sarcode thus budded out one from another, do 

 not become distinctly individualized. Fig. 142, representing 

 the living net- work which remains when the shell of an Or- 

 bitolite has been dissolved, shows the continuity that exists 

 among the occupants of its aggregated chambers. Still, the 

 occupant of each chamber may fairly be considered as homo- 

 logous with a solitary Foraminifer ; and if so, the Orbitolite 

 is an aggregate of the second order : this indefinite marking- 

 off of its morphological units, being the obverse of the fact 

 that the individualities of their prototypes are feebly pro- 

 nounced. Forms of essentially the same kind 

 are aggregated in another manner among the Spongidw. 

 The fibres of a living sponge are clothed with gelatinous 

 substance, which is separable into ^mce&a-like creatures, 

 capable of moving about by their pseudopodia when detach- 

 ed. These nucleated portions of sarcode, which are the 

 morphological units of the sponge, lining all its channels 

 and chambers, subsist on the nutritive particles brought to 

 them by the currents of water that are drawn in through 

 the superficial pores, and sent out through the larger open- 

 ingscurrents produced by ciliated units, such as are shown 

 in Fig. 143. So that, in the words of Prof. Huxley, " the 

 sponge represents a kind of subaqueous city, where the people 

 are arranged about the streets and roads, in such a manner, 

 that each can easily appropriate his food from the water as it 

 passes along." In the compound Infusoria, the 



