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



this having taken place, the restant part of the cell-plasm be- 

 comes separated into two; the inner part changes into a frame, 

 bordering on the dark rhomboid and sending forth processes 

 in two opposite directions, the frame and its processes being 

 successively bright and calcified; the outer part of the cell- 

 plasm remains as a clear envelope of the crystal — ef. text- 

 figur 7: 9. 



• 



Cucumaria elongata and hyiidmani. 



In these two species the crystals present themselves under 

 two phases: rhomboids and stars. The former resembles on 

 the whole those of Cucumaria lactea, thus a detailed descrip- 

 tion of them being superfluous. They are biconvex and 

 vary greatly in length from 11,9 {x to 30,4 [i. Here it deserves 

 to be noted that the rhomboids often present themselves 

 as being more or less anomalous, one or both of their acute 

 angles being bifurcate or even trifurcate (pl. 4, figs. 6 and 7)' 

 In the case of bifurcation the mother-cell can give rise to two 

 overlapping rhomboids (pl. 4, fig. 6). The left picture of fig. 

 7 on plate 4 represents a rhomboid which is rather com- 

 mon and hints at the manner in which a reduplication may 

 be thought to take place. Another noticeable matter of fact 

 may be mentioned, namely that the angles of the rhomboids, 

 instead of being pointed, not seldom have become rounded 

 off; in this case, singularly enough, the contures along the 

 sides of the rhomboid are very sharply marked, while they 

 are very feeble round the angles (pl. 5, fig. 9). Here too, 

 traces of a future second rhomboid can be observed, though 

 the reduplication takes place in a manner somewhat differ- 

 ent from that before mentioned. 



A second crystal-type was said to be the stars which 

 occur in both of the species in question, though they are more 

 sparse than the rhomboids. At first sight I believed them to 

 have been developed in a pure chemical way without co-opera- 

 tion of living organic substance, a supposition, however, that 

 proved to be wrong, the stars as well as the rhomboids having 

 originated in the plasm of living cells. The typic stars are 

 characterized by possessing six short, triangulär rays and their 

 true shape may be best conceived, if imagining that two equi- 

 lateral, triangulär plates have become placed one upon the 



