14 AET. 1. — I. IJIMA : HEXACTINELLIDA, III. 



rays greatly reduced in length (PL II., fig. 2) In extreme cases, 

 this ray may be only about as long as the distal ray and similarly 

 club-like in appearance. So far as the dermal layer is made up 

 of such — so to say, flat — hexactins, it stretches freely over the 

 wide suljdermal space without any spicular connection with the 

 choanosome. Himilarly flattened dermalia, occurring under the 

 same circumstances, have been described by me from RegadrcUa 

 homeyamai among the Euplectellidie (Contrib. I., p. 2G1). 



The dermalia on the back of the sponge-body are all supplied 

 with a proximal ray which is always the longest of the six, the 

 dermal layer on this side being everywhere in close connection 

 with the choanosomal mass. Under a general agreement in ap- 

 pearance, they ditler slightly from those of the frontal lattice in 

 being on the whole larger and in the rays being somewhat more 

 tapering and having a nearly smooth surface except for a short 

 space at the end. Breadth of rays up to 10/^- near the spicular 

 center. iJistal rav 70-100 /'■ Ions; ; swollen towards the rounded 

 end. Paratangentials 220-300 // long. Proximal ray may be 

 twice as long, or longer. 



In the frontal lattice the })aratangentials of separate dermalia 

 are as a rule closely apposed to one another to form the exquisite 

 checker-like latticework (fig. 13). On the back of the sponge 

 this arrangement is carried out to a certain extent but not with 

 the same degree of regularity (fig. 14). Here the separate dermalia 

 generally lie wider apart and at places show no order as to the 

 relative disposition of their paratangentials. 



The gadralia (PI. II., figs. 3 and 16), found in irregular 

 distribution over the gastral surface inside the main osculum, are 

 hexactins. They resemble in a})pearHnce the dermali'a of the 



