i io EVOLUTION IN THE PAST 



of being brought forward from its old central position on the 

 under-part of the body. These creatures must have been 

 living on softer food than their ancestors, for the anatomical 

 alterations had been accompanied by a total loss of the 

 teeth. 



SEA-LILIES Crinoids, or " sea-lilies," after much depression, revived 

 somewhat in the Jurassic ; but their fortunes do not seem 

 to have further improved in the Cretaceous Period. The 

 work of emancipation, however, from a rooted existence 

 was in progress ; and stemless forms were becoming more 

 prominent (Marsupites, Uintacrinus). 



CORALS Reef-building corals were still greatly in force in parts of 

 central Europe. In some regions gracefully branching coral- 

 colonies, resembling the " sea-fans " of our own time, were 

 now to be seen (Gorgoniidce). And red coral is first met with 

 in this Period (Corallium). 



SPONGES Sponges with flinty skeletons were abundant ; and the 

 nodules of flint, found in the Chalk formations, probably 

 represent their remains, increased in volume by the accretion 

 of other flinty materials in the rocks. 



Sponges fortified with six-rayed needles were spreading 

 far and wide (Hexactinellids) ; and species with the needles 

 wrought into elaborate frameworks, and possessing strong 

 roots composed partly of a flinty substance, were much in 

 evidence (Coscinopora, etc). Some of the forms resembled 

 the " Venus Flower Basket " of our own time, and added 

 not a little to the beauty of submarine life (V entriculites). 

 Prosperous also were four-rayed sponges and allied forms 

 (Tetractinellids, Lithisda). Indeed at no other time are they 

 known in such variety. Some of bud-like shape were peculiar, 

 having developed long stalks well rooted at the base 

 (Siphonia). Sponges with lime needles shared for a time 

 the good fortune of their flinty brethren, but towards the 

 close of the Period they met with checks in their onward 

 career. 



PROTOZOANS The lowest forms of animal life Protozoans were well 

 represented by foraminifers and radiolarians. The former 

 must have been as sand-grains in the sea. By appropriating 

 lime held in solution in order to form their shells, and 



