150 THE MECHANICAL FUNCTIONS. 



sponge contracts when touched is of very ancient 

 date, for it may even be traced beyond the time 

 of Aristotle ; and it has been handed down by 

 succeeding naturalists, and echoed from the one 

 to the other, so as to have gained admission, 

 without being questioned, in all the recent syste- 

 matic works on Zoology. 



The alleged spontaneous palpitation of the 

 flesh, occurring in particular parts, had its origin 

 in the views taken of the nature of sponges by 

 Marsigli, an Italian naturalist, who, in the year 

 1771, announced that he had seen movements of 

 dilatation and contraction in the round apertures 

 visible on the surface of sponges. This state- 

 ment, so confidently advanced, seems to have 

 made a strong impression on Ellis, who, while 

 pursuing a similar train of observations, came to 

 persuade himself that he could see, not only the 

 movements described by Marsigli, but also the 

 passage of water to and fro, through the same 

 apertures. He communicated this account to 

 the Royal Society in 1765 ; it was published 

 in its Transactions,* and will ever remain an 

 instructive proof of the degree in which our very 

 perceptions may be influenced by preconceived 

 views, and by the force of the imagination. 

 Pallas immediately admitted, without examina- 

 tion, the hasty assertion of Ellis, into his " Elen- 



* Vol. Iv. p. 284. 



