214 



HYALONEMA (HYALONEMA) PLACUNA. 



less equal, or two larger and four more or less rudimentary rays. If this assump- 

 tion is correct, and if the energy saved in the building of the smaller rays is 

 utilised in increasing the size of the larger, the latter must be hypertrophic to 

 a degree in proportion to the degree of reduction of the former as, in fact, 

 they are. 



The amphidiscs. As these spicules are more numerous in form B than in 

 form A, I shall commence the description of them with an examination of the 

 amphidiscs of the former. 



The amphidiscs of form B are 18.5-3G7 ^ long. The frequency of those of 

 different length is shown in Figure 9. 



Macramphidiscs 

 * 



Micramphidiscs Mesamphidiscs ; ; 



narrow anchors 

 broad anchors 



i05.-<mtoo^oo-*tDcoio^tnC2ooo(N<MCT>ro^Ln 



I.— lT-HCMLr>^HG^O^rH(M[^t^(MC\]00'-<CMOI>-CO'— 1004 



^ t^ ( 



^ ai t^ cc .-H (^ -t ^' CO u^ 

 1~ OD O M lO t- o n <n o 



t I I I I M I M I M I I I I I I I I I I I M M M I I I I I 



00 "^ »-< •— < CV] LO I 



a^orr-— tcqc^f^cMCMoo.— 'CMOt^oo^HO 



LO r^-ooocvimt^oooco 



Fig. 9. — Form B. Amphidiscs. 



The figure shows that, apart from minor depressions of the frequency-curve, 

 the amphidiscs can, biometrically (according to the frequency of those of different 

 lengths), be divided into two main-groups, one comprising amphidiscs 18.5-48 n 

 long, the other amphidiscs 124-367 m- These groups dimensionally so very 

 different are connected only by three of the 96 amphidiscs measured, which are 

 55, 72, and 100 n long respectively. The part of the curve pertaining to the small 

 amphidiscs exhibits three not very deep depressions, the part of it pertaining to 

 the large amphidiscs one small and one considerable depression. The latter lies 

 between amphidiscs 187 and 214 ^ long. 



