578 E. A. MINOHIN. 



rays and ditninution of the third, become modified to form the 

 secondary monaxons, become crystalline much earlier than the 

 more regular triradiates, especially as regards the two rays 

 which are placed in the same straight line to form the shaft 

 of the monaxon spicule. 



Synopsis of Observations. 



The numbers in brackets denote the length in /x of the rays of the spicules 

 observed. Sometimes the rays vary in length, and the two extremes are 

 given. In the case of spicules of the second class in contorta and cere- 

 brum the length given is half the length of the shaft formed by the two 

 rays placed in a straight line. 



s. denotes tiiat the rays were separate, J. that they joined ; while those 

 spicules too much corroded to judge of this point are marked c.^ 



(1) Coriacea, adult. — 3 spicules examined. 2 remained dark (4 s., 

 5 «.) ; 1 lit up feebly (67.). 



(2) Contorta embryo. — 26 spicules examined. 

 Class 1. 



Perfectly dark.— 8 (4, 6^ 7, 12, 13, 13, 16, 18). 

 Faintly illuminated.— 1 (17). 

 Pairly bright.— 4 (16, 17, 17, 17). 

 Class 2. — 13 examined j all lit up. 

 Faintly.— 3 (3, 6|, 6i). 

 Distinctly.— 2 (4^, 71). 

 The rest brilliantly. 



(3) Cerebrum. — 2 embryos. 

 Embryo A. 



Class 1. 

 Perfectly dark.— 13 (9 c, 11 s., 11 c, 11 c, 12 c, 13 s., 14 s., 14 c, 



14 c, 15 s., 15 c, 15—17 5., 16 s.). 



Faint illumination in centre. — 8 (13y., 13^'., 14_;., 14 j., 14_;., 14/, 



14-16/, 15/). 

 Rays faintly illuminated. — 12 (13/, 13 — 15/, 14 5., 14/, 14/, 



14-16/, 14-17/, 15/, 15/, 15/, 16/, 16/). 

 Distinctly illuminated.— 12 (13/, 13—14/, 14—18/, 15/, 15/, 



15 j., 15 j., 16 /, 16 /, 17 /, 17 /, 17 /) 

 Brightly illuminated.— 2 (15 /, 17 /). 



^ Even when the spicule is perfect, it is often very difficult to be certain 

 whether the three clearer lines usually seen at the junction of the rays indicate 

 real interspaces, or lines of recent union. 



