CALYCOSILVA CANTHARELLUS. 75 



have been observed. The lateral rays of these spicules extend paratangentially 

 like those of the larger ones, but are, apart from this, more or less irregularly 

 disposed and Ue anyhow in the meshes of the quadratic network formed by the 

 lateral rays of the large pentactines. 



In most of the pentactines the apical ray is weU-developed, longer than the 

 lateral rays; in some it is reduced and considerably shorter than the laterals. 

 The pentactines with short apical ray appear to be scattered indiscriminately 

 among the pentactines with long apical ray. 



Most of the apical (proximal) rays of the pentactines penetrate and extend 

 beyond the paratangential membranes or networks forming the floors of the sub- 

 dermal and subgastral cavities. The end-part of many transverse rhabds are 

 parallel to and in close contact with proximal pentactine rays (Plate 2, fig. 12b). 



The microhexactines are very rare and have been found only in the regions 

 of the subdermal and subgastral cavities. 



The regular onychhexasters are abundant in the choanosome and in the 

 floors of the subdermal and subgastral cavities (Plate 2, fig. 3; Plate 5, fig. 1). 

 Some also occur in the proximal parts of the columns and threads which traverse 

 these cavities. They are not confined to the body proper of the sponge and also 

 occur in the stalk. These onychhexasters form a series, one end of which is 

 represented by onychhexasters with short and stout end-rays, the other by 

 onychhexasters with long and slender end-rays. The former are found in the 

 proximal parts of the subdermal and subgastral regions of C. c. vars. simplex 

 and helix, but appear to be absent in C. c. var. megonychia. The latter are, 

 in all varieties, plentiful in the interior. Intermediate forms are met with 

 wherever onychhexasters occur. 



The oxyhexasters occur in small numbers in the choanosome of C. c. var. 

 helix and somewhat more frequently in C. c. var. megonychia. 



The helonychhexasters, which occm* only in C. c. var. helix, are met with 

 in fairly large numbers in the floors of the subdermal and subgastral cavities- 

 and are also found in the proximal parts of the columns and threads traversing 

 these cavities. These spicules are not uniformly distributed throughout this 

 region, but in some parts of it are much more numerous than in others. 



The plumicomes are confined to the columns and threads which traverse 

 the subdermal and subgastral cavities and are more numerous in their distal 

 than in their proximal parts. Their paratangential distribution is fairly uni- 

 form. They are quite abundant in C. c. vars. simplex and helix, but very rare 

 in C. c. var. megonychia. 



