THÉEL, THE AMOEBOCYTES BY ECHINODERMS. 37 



Fig. 4. — Another plasma-cell from the same preparation; leiigth 

 = öl [J.. 



Fig. 5. — A fau-sliaped plasma-cell from tlie same preparation, 

 a common type in the echinoderms; length of the whole cell = 85 [).; 

 breadth of the disens = 59 (JL. 



Fig. 6. — Three »amoebocyte with sperules» (= knlamoebocyter) 

 from the same preparation; diameter = from 5,95 {J. to 9,5 \i.; nn- 

 clens = from 2,38 [J- to 3,4 [i. 



Plate 3. 



Coelomic crystals in Cucumaria lactea. 



Figs. 1 — 10. — Digitiferous crystals in different stages of develop- 

 ment varying in length from 22,8 {i to 30,4 [i; the shaded peripheral 

 part surrounding them denotes hyaline protoplasm; drawn from the 

 living. 



Figs. 11 — 14 — Four rhomboids, having a length of from 22,8 (i 

 to 27,8 [J.; drawn from the living. 



Figs. 15 — 16. — Two rhomboids decalcified af ter fixation in Peré- 

 NYi's fluid, stained and mounted in balsam; nucleus very distinct; 

 length = 20 [J,. 



Figs. 17 — 18. — Two digitiferous crystals decalcified af ter fixa- 

 tion in Perénti's fluid, stained and mounted in balsam; nucleus dis- 

 tinct; length = 22,1 {J.. 



Fig. 19. — Khomboid partly decalcified, stained and mounted in 

 balsam; length = 27,2 {J.. 



Fig. 20. — Digitiferous crystal decalcified after fixation in Peré- 

 NYi's fluid, stained and mounted in balsam; nucleus invisible; length 

 = 23,8 [1.. 



Figs. 21 — 22. — Two rhomboids drawn from the living; the shaded 

 peripheral portion represents living plasma with protrusions at the 

 acute angles. 



Fig. 23. — Rhomboid decalcified, stained and mounted in balsam. 



Fig. 24. — Digitiferous crystal fixed in 40 % formalin, stained 

 and mounted in balsam; length 22,8 [i; a well marked rhomboid hav- 

 ing been left after fixation; nucleus elongated and curved. 



Plate 4. 



Coelomic corpuscles in Cucumaria elongata; figs. 1, 2, 6, 7 and 10 

 — 13 are drawn from the living, the rest being fixed, stained and 

 mounted in balsam. 



Fig. 1. — Twelve living red blood-corpuscles of different appear- 

 ances; in some specimens the elongated corpuscles predominate, in 

 other the rounded; their magnitude differs greatly even in the same 

 animal from 19 [JL up to 45,6 [J.; every gradation in size between these 

 two extremes being met with; nucleus jDresent as a round whitish 

 spöt; a number of granules present in the somewhat darker central- 

 portion, often accumulated in the neighbourhood of the nucleus. 



Fig. 2. — Five side-views of the same corpuscles. 



