OF THE SPONGIAD^. . 5 



8. Inhalation and exhalation. 



9. Nutrition. 



10. Cilia and ciliary action. 



11. Reproduction, ovaries, gemmules, &c. 



And to conclude with observations on 



The generic characters ; 

 The specific characters ; and 

 On the method of examination. 



In my references to the views of preceding writers 

 regarding the anatomy and physiology of the Spongiadse, 

 I shall endeavour to correct the errors, rather than to point 

 out the authors of them, feeling satisfied that posterity will 

 care as little about the petty angry discussions concerning 

 the facts and opinions of the present period as we do about 

 those of our ancestors ; at the same time I shall endeavour 

 to do justice to the industry and research of preceding 

 naturalists, whose errors of omission are entitled to every 

 possible excuse, when we remember the difficulties they 

 laboured under in the course of their investigations, for 

 want of competent microscopic powers with which to work 

 out the organization of the minute and delicate objects of 

 their research, while we are in full possession of all the 

 advantages of the modern improvements of the microscope, 

 giving a pleasure and facility to our investigations that 

 must have been comparatively almost unknown to our 

 predecessors. 



THE SPICULA. 



The spicula are essentially difierent in character from the 

 fibres of the sponge, although the latter may be equally 

 siliceous with the former. However closely the spicula may 

 be brought into contact with each other or with siliceous 

 fibre, they do not appear to unite or anastomose, while the 

 fibre, whether siliceous or keratose, always anastomoses 

 when it comes in contact with other parts of its own body 

 or of those of its own species. 



