ART. 12 HEXACTINELLID SPONGES — OKADA 97 



ner at the ends. Slender, sparsely roughened terminals, generally 

 two or three in number, arise from each principal. They are apt 

 to be broken off near the base. It seems that this form is the more 

 abundant of the two varieties. 



In variety A (fig. 12, e) the terminals are considerably stronger, 

 being nearly 5/a in thickness at the base, while the principals are 

 much less distinctly indicated, being in fact quite abortive. They are 

 obscurely rough all over. There are generally two terminals to each 

 principal, never more, rarely only one. The principal measures 

 l72jti in diameter. The hexactinic form (fig. 12, e) is somewhat 

 larger, measuring lOO/x in diameter and having roughly surfaced 

 terminals which are pointed at the ends. The hemihexactinic forms 

 are somewhat smaller, measuring about 150^ across, and are pro- 

 vided with delicate and slender terminals. These two forms are 

 distributed fairly abundantly, intermixing with the normal oxyhex- 

 asters in the parenchyme. 



Discoctasters (fig. 12, g, h, i) are common in all parts, being especi- 

 ally abundant near the ectosome and the endosome. They measure 

 180/x to 220/x in diameter. The principals are 8ja thick at the base, 

 fairly slender, and 40;U. long. The number of principals projecting 

 from the spicular center varies from 6 to 8 ; in most cases 6 and less 

 often 8, of which 6 protrude laterally and the remaining 2 forward 

 and backward. In other cases, the pairs protrude from the spicular 

 center in all directions. The number of terminals in a tuft is 5 to 12, 

 each with a minute terminal disk. They are usually somewhat longer 

 than the principals, measuring 56/a in length, with their tuft narrow 

 at the base and slightly expanded distally. This discoctaster has a 

 distinct quadrangular humplike prominence measuring 20/x in di- 

 ameter on the central node. The terminal disk is very small and 

 pinheadlike. The microdiscohexaster is found abundantl}^ in the 

 parenchyme. Spherical in shape, it is similar in appearance and in 

 structure to that of all members of the genus, so that a special 

 description appears unnecessary. It measures 40ja in diameter. 



The basidictyonal plate (fig. 12, j, k) is represented by a fairly 

 large-meshed siliceous reticulum, the beams of which may measure 

 20;u broad at the widest part and have a smooth surface. In isolated 

 instances much more robust pentactins are found (14/i to 18/i in 

 breadth, and paratangentials 32ju to 48/a in length), and oftener 

 stauractins having nearly the same or a greater axial length. It is 

 not difficult to make out that the foundation of this plate is formed of 

 the stauractins and pentactins above mentioned, which are directly 

 as well as synaptically fused together. 

 118040—32 7 



