82 I. IJIMA : HEXACTINELLIDA. I. 



full number at a very early period of life. With the growth in 

 girth of the sponge, the beams in question become wider and 

 wider set apart from one another, and if increase in their number 

 takes place at all in the said region, it can not be to any con- 

 siderable extent. An end is definitely put to their shifting asunder 

 or their new formation by the soldering together of spicules, 

 which process, as already mentioned, sets in at the sponge-base 

 when the entire body has attained a length of about 200 mm. 

 Quite a dififerent circumstance should obtain in the upper region. 

 With the growth of the body, many of the ever elongating 

 longitudinal beams undergo splitting at indefinite positions in the 

 circumference but especially frequently near the upper end to- 

 wards the close of the growth, when that end becomes the 

 broadest part of the entire body. 



With respect to the increase in number of the transverse 

 beams, the facts ascertained by F. E. Schulze ('95, p. 2")) from 

 E. simplex find corroboration in the present species. The most 

 active seat of their multiplication is the upper end of the sponge 

 close to the cuff, where they lie most closely together and are 

 thinnest, being composed of slender and evidently young 

 parenchymalia. Here the sponge-wall is youngest at all stages 

 of its growth and the formation of new transverse beams may be 

 said to be constantly taking place until the sponge has nearly 

 reached its full length. After the expansion of the upper end 

 into the broadest part of the wall, there no longer exist signs of 

 their new formation. 



The lower extremity of the body proper is, as already re- 

 marked, blindly closed at first and apparently lies free above 

 the surface of the substratum, the sponge being rooted by the 

 basal spicules only. Soon the condition changes. By the time 



