84 



BIOLOGICAL SURVEY OF 



figured these. In all cases fifty or more spicules have been 

 measured and the mode ascertained. This was considered 

 best, as in this way the subtle differences in the size of spic- 

 ules distinguishing some of the species (^varieties?) are 

 disclosed, whereas such are hidden when only the extremes 

 of length are given. The latter, however, is the usual method. 



The size of the spicules is frequently shorter in the speci- 

 mens from this region than it is in those reported from farther 

 north, but this is only what might be expected, as the evidence 

 from the geographical distribution of most of these species 

 would indicate that they are northern, Arctic forms and in 

 the Mt. Desert Region these species may be near their south- 



