192 



HYALONEMA (HYALONEMA) AGASSIZI. 



To attain a clearer insight into the range and character of the variation of 

 the length of the large macramphidiscs in the four forms of this sponge I drew 

 the following graph, in which the frequency of the large macramphidiscs of 

 various lengths of all the four forms is represented. To make the curves in it 

 commensurate I calculated the relation of the number of large macramphidiscs 

 actually measured to 100, that is its percentage in each form, and multiplied all 

 the numbers of amphidiscs belonging to the same category, in respect to length, 

 by this number. These percentages are represented by the curves in Fig. 6. 



Frequency 

 (%) 



--- CO 



a. o 



•5 



C 



.2 



c o 



Fig. 6. — l^arge macramphidiscs. 



The above curves, expressing the relative frequency of the large macramphi- 

 discs of different lengths in the six forms, are based on 247 measurements. The 

 curves pertaining to all the forms, except D, have one main elevation, the curve 

 pertaining to form D has two. The second main elevation of this curve coin- 

 cides with the main elevations of the curves of forms B and C, and with the 

 considerable right secondary elevation of form E. All four lie at a point corre- 

 sponding to amphidiscs about 240 n long. The main elevations of the curves 

 of forms A, E, and F lie at points representing spicules about 200 m long. The 



