ART. 12 HEXACTINELLID SPONGES — OKADA 81 



distal or proximal ray. The rays are nearly uniformly broad 

 through their length toward the conically pointed and microtuber- 

 culated end. These hexactins, being single or two or three in a 

 group, also form a regular quadrate latticework, the length of 

 which is nearly the same as those of the dermal layers or 110/u, to 

 145ju. Besides these large hexactins, there occasionally occur small 

 and delicate hexactins (fig. 9, g), which may be younger or not fully 

 developed, with lengthened paratangentials, 80/*; distal ray, 75|u; 

 and proximal ray, 90/i. 



In this specimen I have occasionally found paratangentially 

 disposed, diactinic dermalia (fig. 9, h) and diactinic gastralia. The 

 manner of their occurrence in company with the stauractinic or 

 pentactinic form in the ectosome and with the hexactins in the 

 endosome leaves no doubt as to the legitimacy of considering them 

 to be dermalia and gastralia. They seem to be linked to the hypo- 

 dermalia and the hypogastralia by means of intermediate forms. 

 Their presence in the species seems to be nearly constant. 



Of the hexasters, the oxyhexaster (fig. 9, ?, j, k) is of frequent 

 occurrence in the endosome and the ectosome, as well as in the 

 choanosome. The oxyhexaster exhibits the normal oxyhexaster as 

 well as hemihexactinic and hexactinic forms. The normal oxyhex- 

 asters may be distinguished as of two kinds, the smaller one (fig. 9, 

 ?, i) is usually present in the ectosome and in the endosome of the 

 superior region of the entire stock, while the larger one (fig. 9, A ) 

 seems to occur in the parenchyme of the inferior basal regions. 

 They differ in respect to both size and general appearance. The 

 former is comparatively small and of a delicate appearance, with a 

 diameter of 120)u to 130/*. From each exceedingly short and slender 

 principal arise two or three thin, straight terminals, the surface of 

 which is rather sparsely tuberculated. The latter oxyhexaster is 

 larger, with much stronger terminals, measuring 76/i in length. 

 The principals are usually fairly long and broad, 8/t at the base. 

 The number of terminals to a principal is usually two or three. The 

 diameter is 150/x to 160/*. Its entire surface is strongly tuberculated. 



Hemihexactinic and hexactinic forms (fig. 9, k) are of frequent 

 occurrence. In shape and size they quite agree with those of A. 

 schnlzei. 



The macrodiscohexaster in this species is somewhat smaller than 

 that of .1. schulzei, usually measuring 250/i to G50/* in diameter, 

 about half that of the latter species. The central sphere measures 

 35/* to 48/* in diameter. The terminals are delicate, slender, rodlike, 

 and quite smooth-surfaced. The terminal disk is somewhat con- 

 ically convex on the outer side. The margin shows a row of num- 

 erous small teeth. This spicule occurs usually in the hypoderm and 

 in the dermal membrane, as well as occasionally in the parenchyme. 



118040—32 6 



