ERYLUS SOLLASII. 



287 



merely due to differences in the amount of light to which the different speci- 

 mens were exposed during life. I am therefore inclined to consider these 

 differences as direct individual adaptations of the simplest kind to which no 

 systematic importance whatever can be attached. 



The chief differences in the spiculation of the six forms is shown in the 

 following tabular view of the averages of the three largest observed of the most 

 important spicule dimensions and of the character of the triaene-cladomes and 

 aspidasters. 



Race 



I 



11 



III 



Form 



A 



B 



C 



D 



Rhabd megascleres 



length, /t 



630 



710 



747 



853 



743 



913 



thickness, /< 



12 



13 



23 



20 



19 



21 



Microrhabds 



length, ji 



6.5 



54 



56 



62 



58 



44 



thickness 

 of tyle, /( 



5.8 



4.8 



5.7 



5.7 



5.2 



5.4 



Triaenes 



rhal)dome 



length, /( 



373 



290 



397 





380 



490 



thickness /t 



13 



10 



18 



21 



1 o 



i\) 



O 1 



cladome 



breadth, /( 



373 



413 



457 



450 



417 



530 



ciiaracfer 



all cladcs 

 sim|>le 



most clades 

 simple, some 

 branched 



most clades 

 branched 



most clades 

 simple, some 

 branched 



most clades 

 branched 



Acanthtylastcrs 



diameter, ji 



33 



29 



31 



29 



35 



33 



Aspidasters 



length, /( 



120 



118 



128 



124 



152 



1.50 



proportion of 

 letigtli to breadth 

 to thickness 



100: 

 55.3:8.2 



100: 

 .59.1: 



9 



100: 

 57: 

 8.4 



100: 

 56:9.8 



100: 

 49.8: 7.G 



100: 

 57 7: 10 



character 



few irregular, four 

 to six ray-spines 



many 

 irreg- 

 ular, 

 four 

 to six 

 ray- 

 spines 



few irregu- 

 lar, four to 

 si-x ray- 

 spines 



few irregu- 

 lar up to ten 

 ray-spines 



few irregu- 

 lar, four to 

 six ray- 

 spines 



This table shows that in race I, form A, all the triaene-clades arc simple; 

 and the rhabd megascleres shorter and thinner, the microrhabds longer and 

 thicker, and the triaene-cladomes smaller than in any of the others. In race I, 



