Studien am Skelet der Echinodermen. 



57 



Heterocentrotus mamillatus; Stachel senkrecht zur 

 optischen Achse geschliffen. 



a f = 51°59' N D21 o= 1,87747 t=21° 



log a £ = 9,89643 — 10 

 log N = 0,27357 

 logn =0,17000 



III. 



n £D21 o = 1,47911 



*« caicit = 148640 



n £ Echin. = 1,47911 



Differenz = 0,00729 



M Opt. Achse 



Lichteinfall 



Licht 



Opt.Achse 



Fig. D. 



Fig. E. 



Heterocentrotus mamillatus; Stachel parallel zur 

 Achse geschliffen. 



a £ = 51°58' N D21 o= 1,87747 t = 21° 



log sin a = 9,89633 — 10 

 log N = 0,27357 

 log n = 0,16990 



IV. 



n fD21 o = 1,47877 



n.caicit =1,48640 

 n £ Echin. =1,47877 

 Differenz = 0,00763 



Heterocentrotus mamillatus, Stachel. 



a f = 51°58' N D 21 o = 1,87747 t = 21° 



log sin a s = 9,89633 — 10 

 log N = 2,27347 



logn £ 



0,16990 



