62 AKT. 7. 1. IJIMA : IIEXACTINELLIDA, IV. 



or iieurly «traiglit. F. E. Schulze does not niciition these 

 liexactins in liis descriptions but lias not omitted tliem in his 

 figure (Chall. Ive})., PI. LXI., fig. o) ; indeed I observe their 

 ])resence in the preparations from Celju specimens. Such par- 

 enchymalia are known to exist not only in (_[ meyeri, l)ut also 

 in the su1)species iuhcrom of the same as well as iu C. thierfel- 

 (leri. In the remaining members of the genus they seem to have 

 disap})eared altogether, leaving the 2)arenehymalia composed ex- 

 clusively of diactins, so fir at least as those of the sponge-l)ody 

 are concerned. 



In the upper one-third of the stalk the jnirenchymalia seem 

 to consist only of longitudinally disposed diactins which are dense- 

 ly grou2)ed together but free. Synapticular connections between 

 them commence to occur at about the beginning of the lower 

 two-thirds of the stalk. At the same time there begin to a|)pear, 

 among the diactinic parenchymalia of the region, small hexacti- 

 nic — and occasionally pentactinic — elements (PI. IV., fig. 8), the 

 j'ays of which are comparatively short and thick, have rounck'd 

 ends and show inconspicous microtubercles on the surface either 

 all over or near the ends only. The spicules in question are at 

 Jii'st free but soon l)ecome fused to one another as w^ell as to the 

 diactinic parenchymalia of the region in irregular orientation. 

 Consequently, in about the middle of the stalk the skeleton is 

 already entirely represented by a dense and stony siliceous frame- 

 work, except for isolated oxyhexasters lying loose in the meshes. 

 The small hexactins just mentioned I regard as homologous with 

 those which I have called the bdsiJiclijoJialiff in other lyssacine 

 Hexactinellids. Tliey have l)een mentioned and well figured by 

 Y. E. Schulze (Chall. Eep., PI. LXL, figs. Ö, 6 cV: 8). 



