Oy THE SPONGIAD^. 117 



one observed by Dr. Grant, Halichondria incrmtans, John- 

 ston, the oscula being few in number and very large, the 

 excurrent streams are more than usually powerful. In the 

 course of my investigations " On the Vitality of the 

 Spongiadse," at Tenby, which are published in the ' Reports 

 of the British Association' for 1856, and in the "Further 

 Report," published in the same work for 1857, I have, 

 described a long series of observations of the vital actions 

 of the Spongiadse as displayed in Hymeniacidon caruncula 

 and 8j)ongilla fimiatilis, in both of which species there was 

 a perfect accordance in the habits and modes of exertion of 

 these vital actions. 



The power of inhalation appears to be exerted in the 

 Spongiadse in perfect accordance with the similar vital 

 functions in the higher classes of animals, not involuntarily 

 and continuously as in the vegetable creation, but at inter- 

 vals, and modified in the degree of its force by the instincts 

 and necessities of the animal. And it may be readily seen 

 that the faculty of inhalation is exercised in two distinct 

 modes ; one exceedingly vigorous, but of comparatively 

 short duration, the other very gentle and persistent. In 

 the exertion of the first mode of inhalation, that is during 

 the feeding period, a vast number of pores are opened, and 

 if the water be charged with a small portion of finely- 

 triturated indigo or carmine, the molecules of pigment are 

 seen at some distance from the dermal membrane, at first 

 slowly approaching it, and gradually increasing their pace, 

 until at last they seem to rush hastily into the open pores 

 in every direction. In the meanwhile the oscula are widely 

 open, and pouring out with considerable force each its 

 stream of the excurrent fluid ; and if the reflection of one 

 of the horizontal portions of a window-frame be brought 

 immediately over an excurrent stream, it will frequently be 

 seen that the surface of the water is considerably elevated 

 by its action, even although the osculum be half or three 

 fourths of an inch beneath its surface, and this vigorous 

 action will sometimes be continued for several hours, and 

 then either gently subside or abruptly terminate. Occa- 

 sionally a cessation of the action may be observed in some 



