PLATE 106. 



Euretid. Station 4641. 

 Figiu'es 1-3. 



1. — Part of the gastral face of the skeleton of the tube-wall; magnified 30; phot. Zeiss, planar 20 mm. 



2. — Part of the dermal face of the skeleton of the tube-wall; magnified 30; phot. Zeiss, planar 20 mm. 



3. — View of the skeleton; natural size; phot. Zeiss, anastig. 480/412 mm. 



Hyalonema (Prionema) crassum Lendenfeld. 

 Figm-es 4-37. 



4-12. — Microhexactines; magnified 200; phot. Zeiss, apochr. 8, compcns. oc. 6: 

 4-6, the same microhexactine ; 



4, focussed high; 5, focussed on the centre of the spicule; 6, focussed low; 

 7-10, different microhexactines; 



11, 12, a group of microhexactines in a spicule-preparation ; 

 11, focussed higher, 12, focussed lower. 

 13-20. — Micramphidiscs; magnified 500; pht)t. Zeiss, H. I. apochr. 2, compens. oc. 4. 

 21-25. — Micramphidiscs; magnified 2000; u. v. phot. Zeiss, q. monochr. 1.7, q. oc. 10: 

 21-23, the same micramphidisc; 



21, focussed high: 22, focussed 0.7 n lower; 23, focussed 1.4 ^ lower; 

 24, 25, two different micramphidiscs. 

 26-30. — Pinnies; magnified 300; phot. Zeiss, apochr. 8, compens. oc. 12. 



31. — A microhexactine (of which only two opposite rays are in focus); magnified 500; phot. Zeiss, 



H. I. apochr. 2, compens. oc. 4. 

 32-37. — Rays of microhexactines; magnified 2000; u. v. phot. Zeiss, q. monochr. 1.7, q. oc. 10: 



32, the basal quarter of a ray, focussed low; 



33, the basal half of the same ray, focussed higher; 34, focussed still higher; 



35, the distal thii-d of the same ray focussed highest; 



36, the tip of another ray; 



37, another ray. 



