THÉEL, THE AMOEBOCYTES BY ECHINODERMS. 39 



Figs. 19 — 20. — Six prisms from the coelomic cavity of Meso- 

 thuria intestinalis; drawii from the living; length from 7,6 {J. to 15,2 [J.. 



Fig. 21. — Five red blood-corpuscles from the coelomic fluid of 

 Cucumaria hyndmani, drawn from the living; length =17 to 19 [J-. 



Fig. 22. — Two red blood-corpuscles of the same animal, fixed 

 in 40% formalin, stained and momited in balsam; magnitude = 17 u.. 



Fig. 23. — Four red blood-corpuscles of the same animal, fixed 

 in Perényis's fluid, stained and mounted in balsam. 



Plate 6. 



Orystals or spicula from the coelomic cavity of Psolus phantapus. 

 Figs. 1 — 14 drawn from the living; figs. 15 — 20 fixed, stained and 

 mounted in balsam. The shaded parts of figs. 1 — 14 denote surround- 

 ing peripheral protoplasm. Length of the spicules = from 60,8 ll to 

 64,6 [J.; length of the rhomboids = 11,4 [J. to 22,8 ^; diameter of the 

 stars = 11,4 [JL to 15,2 (JL. 



Fig. 1. — Two side-views of two spicules. 



Fig. 2. — Upper view of an outgrown spicule, the growth of the 

 spire or crown having been restrained. 



Fig. 3. — Upper view of a not fully outgrown, irregular spicule 

 with four arms. 



Figs. 4 and 5. — Upper views of well developed spicules. 



Figs. 6 — 8. — Developmental stages of spicules == the central 

 crowns. 



Fig. 9, — A singular specimen of spicules with the two opposite 

 arms terminating in a minute rhomboid. 



Fig. 10. — Upper view of a spicule with four arms. 



Fig. 11. — A typical står. 



Fig. 12. — A typical rhomboid. 



Figs. 13 and 14. — Upper view and side-view of a rhomboid 

 enclosed within the globular mother-cell. 



Figs. 15 — 20. Three spicules, two romboids and one står, fixed 

 and stained; fig. 18 = side-view of a spicule; the nucleus is very dis- 

 tinct in all except in the står. 



Plate 7. 



Coelomic corpuscles in Mesothuria intestinalis, fixed in 40 % for- 

 malin, stained by Heidenhain's iron-alum haematoxylin method and 

 mounted in balsam. |,When the coelomic fluid has been removed from the 

 animal into a long tubular glass, it separates rapidly into two parts: — 

 a whitish meshy coagulum macje up either of long strings and fine 

 interlacing filament of fibrin or of more expanded masses — and a påle 

 liquid. An examination of a sample of the coagulum proves that most 

 of the amoebocytes either are attached to the coagulum or may be 

 found free in its meshes, while the rest has sunk to the bottom. The 

 figures on this plate are drawn from a sample of the coagulum, kept 

 during 12 hours in a tubular glass. 



