22 ARKIV FÖR ZOOLOGI. BAND 13. N:0 25. 



fig. 3). After the preparation having been washed with a solution 

 of iron-alum, the blood-cells show a different aspect; the num- 

 berless fine granules ha ve disappeared and given place to a fewer 

 number of somewhat larger granules of two different exteriörs: 

 6ZacÄ:-coloured, slightly larger and fewer, seemingly identical 

 with the colourless granules in living cells; and ivhite granules, 

 invisible in living cells (pl. 4, fig. 5). Not seldom blood-cor- 

 puscles, prepared in this way, occur which show such an abund- 

 ance of white granules, that they give the impression of being 

 perforated like a sieve. 



When fixed with formaldehyde in solution, the corpuscles 

 of the polian vesicle lose their elongated form and become 

 concentrated and roundish oval; owing to the quality of the 

 fixative, a number of light bleb-like protuberances of clearer 

 protoplasm has been forced towards the circumference (pl. 

 4, fig. 4). In this connection it may be noted that here, quite 

 as in Thyone fusus, the polian vesicle contains a lot of small 

 clear bodies resembling dröps of oil, probably derived frorr^ 

 an abnormous process of budding and releasing. 



Cucumaria hyndmani. 



As to the red corpuscles of this species, I have only to 

 refer to what has been said with regard to those of the pre- 

 ceding one. However, it ought to be added, that they reach a 

 length of only 17 to 19 ]x and that they are fewer in number, 

 causing the coelomic fluid to become less intensively red- 

 coloured, or, now and then, almost colourless. Here even they 

 are slightly concaved with the edge lighter than the middle; 

 their nucleus is hardly visible in living cells. 



Mesothuria intestinalis. 



Having made my observations on the blood-corpuscles of 

 this species on fixed and stained objects only, my information 

 of them is very superficial. On the whole, I have examined 

 them in preparations of fibrin-like matters, adhering to their 

 filament, net-work or films, together with the plasma-amoe- 

 bocytes mentioned afore. In a suitably treated preparation 

 of a coagulum, they are often massed together into groups, 

 which become almost black by staining with iron-alum hae- 

 matoxylin. 



In general, the blood-corpuscles have a rounded or oval 



