90 ANATOMY AND PHYSIOLOGY 



could not by the closest observation detect these motions, 

 which are so readily to be seen at other periods of their 

 existence ; and even at the same period of the year the 

 sarcode of some specimens exhibit these motions, while in 

 others they could not be detected. I have often sought for 

 these phenomena in portions of the sarcode of Halichondria 

 panicea, Hymeniacidon caruncula, and other marine species, 

 but I have never yet been fortunate enough to detect them. 

 It is highly probable that the capability of such notions 

 exists in the sarcode of these and other marine species for a 

 hmited period, but it does not appear that such powers of 

 motion are a constant condition of this substance. 



THE SABCODOUS SYSTEM. 



The physical characters and the peculiarities of the 

 sarcodous matter of Spongilla has engaged the attention of 

 naturalists of late years to a considerable extent, and its 

 inherent vitality and mobile powers have long been known 

 and treated on by many eminent observers ; but its general 

 functional powers in the marine Spongiadae have scarcely 

 received that amount of attention that their importance in 

 the system of the animal demanded. With a view of 

 assisting in the elucidation of these phenomena, I com- 

 menced a series of experimental researches on the ' Vitality 

 of the Spongiadae' in the spring and summer of 1856, at 

 Tenby, where I had every facility for continually observing 

 them in a living and healthy state ; and the results of these 

 observations are published in detail in the reports of the 

 British Association for the years 1856 and 1857, at the 

 special request of the Natural History Section. It is 

 unnecessary, therefore, to repeat these observations here, 

 and I shall confine myself accordingly to a few general 

 conclusions arising from the facts developed by previous 

 observations and by my own experiences as detailed in 

 these reports. . In thus considering the subject, and on 

 comparing the sarcodous system as it appears in the Spon- 

 giadae with its structure and functions in other and higher, 



