PART I. 



MECHANICAL FUNCTIONS. 



THE lowest orders of the animal creation possess 

 neither bones, nerves, sight, or hearing. Some of them 

 are fixed, while others have the power of locomotion, 

 though they possess neither eyes nor ears to direct them 

 in their movements. 



Some of the medusa tribes can hardly claim the rank 

 of organized beings, appearing when alive like a trans- 

 parent jelly, and when dead leaving nothing but a lim- 

 pid watery fluid into which they dissolve by decompo- 

 sition. 



The sponges have no higher place as animal existen- 

 ces, being fixed to the bottom of the sea, and having no 

 sensation and no motion, except that by which they ob- 

 tain their food. 



Many other orders, as the'Hydra, Vorticella, and Infu- 

 soria, are but little removed from these in organization 

 or capacity. Some of these tribes are so little above 

 vegetables in their organization, that they may be pre- 

 served like the seeds of plants. The Rotifer, or wheel 

 animal, which lives and moves in water, may be taken 

 out and dried, when it appears like a grain of dust, and 

 may so be kept for any length of time. But if placed 

 in a drop of water it soon shows its vitality by its brisk 

 voluntary motion, and this alternate life and death the 

 little animal passes through any number of times without 



What is said of the senses of the lowest orders of animals'? What is 

 said of the medusa T: What is said of the sponges 1 What is said of the 

 rotifer, or wheel animal 7 ? 



