THÉEL, THE AMOEBOCYTES BY ECHINODERMS. 21 



Cucumaria elongata. 



The blood-corpuscles of a påle reddish-yellow colour 

 are numbeiiess, causing the fluid of the coelomic cavity and 

 water-vascular system to become red in a higher degree than 

 in SbUj other holothurid examined by me. The red colour 

 shines through the brownish skin at the ends of the animal, 

 where it is less contracted and, consequently, somewhat 

 t hinner. 



The blood-cells vary greatly in form and size. They 

 are more or less irregularly discus-shaped, rounded oval, elon- 

 gated or fusiform and not seldom slightly curved; some of them 

 occur, which are cleft or forked at one end, others ha ve a lobe- 

 like prominence at their middle. A few minutes af ter their 

 removal from the animal into a microscope chamber their 

 contour becomes as if it were wrinkled or erose. They are 

 evidently slightly biconcave, the edge being somewhat thicker 

 and lighter than the middle. The great variation in form 

 hints at a power of feeble amoeboid movement, though I was 

 unable to state to a certainty the existence of such a move- 

 ment in fresh cells. However, it ought to be noted that I oc- 

 casionally met with elongated corpuscles having a minute 

 finger-like protrusion of clear plasm at one end. 



The magnitude of the corpuscles differs greatly, varying 

 in length from 13 [x to 45,6 [i, and every gradation in size 

 between these two extremes may be met with. The rounded 

 oval corpuscles are the shortest, the elongated reacliing the 

 greatest length and being in majority, too (pl. 4, figs. 1 and 2). 



In living state the nucleus of the cells is shown as a round- 

 ish, whitish spöt, varying in position; suitably fixed and 

 stained, it appears in a very distinct manner, its contour 

 being sharply marked. Almost without exception the blood- 

 cell lodges a set of refractile granules, varying in number and 

 changing in colour from whitish to yellow or reddish, a change- 

 ableness which seems to be due to different focussing. Often 

 the granules have their place close to the nucleus, isolated or 

 in small heaps. Now and then they disappear from sight 

 which may depend on certain movements in the cell-plasma. 



After treatment with formaldehyde, Perényi's liquid or 

 other fixatives, and staining by Heidenhain's iron-alum hse- 

 matoxylin method, the blood-corpuscles appear to lodge a 

 great deal of minute granules, isolated or in heaps (pl. 4, 



