86 CALYCOSILVA CANTHARELLUS. 



It seems very probable that they have been produced by a further development 

 of the onychhexasters in the direction of small forms with recurved terminal 

 spines, or large forms with upward directed terminal spines. I think that the 

 forms described above, in which the end-rays appear to be angularly bent near 

 the end, have been developed out of large onychhexasters by a reduction of the 

 number of the terminal spines to one, and by a further increase of the angle 

 at which this single remaining spine arises from the end-ray. The bent terminal 

 part which appears as the distal end of the ray is, according to this, not a part 

 of the end-ray at all, but a terminal spine. When, by a further development 

 in this direction and a further increase of the angle between the terminal spine 

 and the end-ray, this angle becomes 180°, an apparently true oxyhexaster is the 

 result. 



That the oxyhexasters are to be considered as such ultra-end forms of the 

 onychhexaster series is corroborated by the fact that they are larger than the 

 largest regular onychhexasters found in the same variety. 



In the not spirally twisted irregular onychhexasters (Plate 3, figs. 2, 3, 6, 7), 

 which are very rare, the end-rays only or both the end- and the main-rays may 

 be irregular. The onychhexaster (Plate 3, figs. 6, 7) is an example of the former 

 case. In this spicule, which was found in C. c. var. simplex, the main-rays are 

 regularly disposed, equal, abnormally stout, 7 ^ long, and 5 m thick. Each 

 main-ray bears only one or two somewhat irregularly curved end-rays, which 

 are also abnormally stout, being 2-3 fx thick at the base. The terminal spines 

 are 3 m long and recurved. The whole spicule measures 74 n in maximum diame- 

 ter. The onychhexaster (Plate 3, figs. 2, 3) is an example of the latter case. 

 In this spicule, which was found in C. c. var. helix, two opposite main-rays, lying 

 in a line, are considerably longer than the other four, and the end-rays are not, 

 as is invariably the case in the regular onychhexasters, arranged in a verticillate 

 manner at the end of each main-ray, but arise from them at various points. 

 The main-rays are 4 ix thick, the end-rays basally 2 ti. The terminal spines are 

 irregularly disposed, and 3-5 m long. The whole spicule is 89 // long and 64 ii 

 broad. I consider these rare, not spirally twisted, irregular spicules as mere 

 pathological abnormities. 



The helonychhexasters are onychhexasters in which most end-rays or all of 

 them are spirally twisted. To this spiral twisting the name I have given these 

 spicules refers. The helonychhexasters are quite abundant in C. c. var. helix, 

 but absent in the other two varieties. 



The helonychhexasters of C. c. var. helix (Plate 2, fig. 3b; Plate 3, figs. 8-20) 



