THÉÉL, THE AMOEBOCYTES BY ECHINODÉRMS. 33 



other, their angles forming the six radiately arranged rays. 

 Their diameter varies from 11,4 {x to 19 jx. Not seldom defect- 

 ive stars occur, the development of one or several raj^s having 

 been suppressed (pl. 4, fig. 7 and pl. 5, fig. 8). — 



Thyone fusus. 



The crystals have the shape of rhomboids similar to those 

 of the two preceding species; of ten they show five refracting 

 granules, one in the centre and one in the neighbourhood 

 of each angle. No stars have been observed, though I cannot 

 be sure of their being totally absent. 



Psolus phantapus, 



Three types of crystals are to be observed in the coelomic 

 fluid of this species, one of them being entirely characteristic 

 and bearing some resemblance to those of Cucumaria cane- 

 scens, figured by Semper in his work on the holothurids from 

 the PhilijDpine Islands. The two remaining ones, rhomboids 

 and stars, are similar to those in Cucumaria elongata and 

 hyndmani, and therefore I confine myself to a reference to 

 my account of them. 



The third, most conspicuous type is represented by bodies, 

 which present a puzzling conformity with true spicules, such 

 as may be found in the skin of certain holothurids etc The 

 magnitude of these »spicular crystals» surpasses that of all 

 other crystals examined by me, the distance between the points 

 of two opposite spines amounting to 64,0 \l. They consist of 

 a central, more or less irregular crown, typically provided 

 with five triangulär lobes directed outward (pl. 6, figs. 4, 5, 

 20); this crown represents the first stage in the development 

 of the crystals in question. Låter on, generally three long 

 spines grow out from the lower sides of the crown (pl. 6, figs. 

 2 and 4). Among the typic crystals plenty of irregular forms 

 are met with. Singularly enough, in young specimens, which 

 scarcely measure 1 cm. in length, the crystals are quite as 

 numerous and as large as in old and big forms. 



The cell-plasm surrounding the crystals presents itself 

 as a web, more or less expanded between the spines — ef. the 

 figures on plate 6. Worthy of notice is the property of the 

 plasma to move, its main-portion shifting along the central 

 part of the crystals and along their spines, thus causing them 

 to turn round and change posture. 



Arkiv för zoologi. Bd 13. N:o 25. 3 



