28 , G.H. Parker 



ing the current, some with these openings away from the current, 

 and others sidewise to the current. After three days none of 

 these had materially changed their directions, thus giving no evi- 

 dence of a general movement of the body. 



I also attempted to get evidence of the general movement of the 

 body through geotropic responses. Stv'lotella ordinarily grows 

 with its fingers and oscula directed upwards, as though it was 

 negatively geotropic. A large colony was, therefore, kept in- 

 verted in an aquarium of circulating seawater for about a week 

 on the assumption that the fingers might turn from this unusual 

 position, but at the end of this period there was no apparent 

 change of position. This observation, however, does not prove 

 that St\lotella is not geotropic. Slight evidence of geotropism 

 is to be found in its method of regenerating oscula. When a 

 moderately long finger of Stylotella is cut off and the whole of 

 its oscular end, removed, the cylindrical body thus resulting will 

 under favorable conditions form a new osculum. Whether tnis 

 regeneration w^ill take place at the end nearer or farther from the 

 former osculum seems to depend chiefly on the position of the 

 piece of sponge in reference to gravity. If the end that was 

 nearer the former osculum is uppermost, it alwa} s regenerates 

 the new osculum; if it is down, the opposite end very generally 

 regenerates the new organ. Thus in the regeneration of the 

 osculum Stylotella shows some slight geotropic activity, and while 

 it must be admitted that the common flesh of this sponge is con- 

 tractile, this contractility does not seem to result in movements 

 of the body as a whole such as might be looked for in geotropic 

 and other like responses. It is possible that in this sponge the 

 skeleton, which is well developed, is too resistant to allow the 

 body as a whole to be bent, and that, therefore, the contractility 

 of the common flesh can make itself manifest only in the local 

 ways already mentioned. 



D. Currents 



The currents of sponges, which were supposed by many older 

 naturalists to reverse in their direction from time to time and to 

 depend upon a systole and diastole of the body of the sponge, have 



