CHORD ATA — VERTEBRATA — OSTRACODERMS 337 



24. What is the source of the bodily waste and how is it 

 excreted ? 



25. What coordinates the various parts of a muscle, or the 

 different muscles or organs, so that they work together ? 



26. Describe briefly the central nervous system ; the periph- 

 eral system. 



27. What in general would be the path of a nerve impulse 

 passing from the intestine to the brain ? 



28. Describe the passage of light from its entrance into the 

 eye of a vertebrate to its perception by the brain. 



29. What are sclerotic plates? Where developed and in 

 what animals? 



30. Besides sight, w^hat other senses does a cat possess? 

 Where is each located ? 



31. What is meant by the Amniota ? 



32. How are cats nourished before birth? How after birth? 



33. Why are cats called mammals ? 



Class A, Cyclostomata 



Degenerate eel-like fishes, without functional jaws but with a 

 round, sucker-like mouth (whence the name from Greek cuclos, 

 a circle, + stoma, mouth). Paired fins absent. 



It is doubtful if the Cyclostomata are known from the Paleo- 

 zoic, though Palaeospondylus of the Devonian of Scotland, about 

 two inches long with an eel-shaped body, may be a cyclostome. 

 Existing forms are the lamprey-eels and hag-fishes. 



1. Which of the two sub-divisions of the Vertebrata have 

 known fossil representatives ? 



2. Name the seven classes into which the Craniata are divided. 



3. Give distinguishing characters of Class Cyclostomata, also 

 a living and a possible fossil example. 



Class B, Ostracodermi 



Entirely fossil. No trace of backbone or of ordinary jaws 

 present ; mainly because of this absence they are by some re- 

 moved from the Vertebrata and placed in the phylum Arthro- 

 poda. They are characterized by the wonderful development 



