AKT. 4 SPONGES OF CALIFORNIA. de LATJBENFELS 41 



spicules with little protoplasm. In the body this is surrounded by 

 gross chambers 1 to 2 mm in cross section diameter, and much longer 

 in the direction of the axis of the sponge. In one specimen at least 

 there are just four of these, very symmetrically arranged. The 

 outer wall around the above described structure is about 1 mm 

 thick, and like the partitions is packed with felted, interlaced 

 spicules in confusion. The surface, as mentioned above, is thickly 

 studded with protriaenes, clads outward, arranged to a certain ex- 

 tent in brushes but not erect. One may presume the inhalent open- 

 ings lie between these tufts. The oscule is often apical in this 

 form. Several sponges of this form were collected by the Univer- 

 sity of Southern California on November 28, 1914 (U.S.N.M. No. 

 21389) and by myself (the specimens unfortunately were lost) in 

 the autumn of 1923. On both these occasions the massive form 

 was present in greater abundance than the clavate. 



Figure 18. — Tetilla mutaMis de Laubenfels, X300. A, Either 

 end of the oxeas, or the esactinal end of any of the triaenes ; 

 B-D, prodiaenes and protriaenes ; E, anatriaenes 



II. Structure of the massive form: Unlike most Tetillas there is 

 no central or radiate skeleton, instead the spicules are matted to- 

 gether in sheets or walls around gross chambers. The surface, as 

 mentioned above, is crowded with brushes of spicules, usually lying 

 almost flat and practically never erect. 



Ectosomal spicules, prodiaenes and protriaenes (fig. 18, B, C, D) ; 

 rhabd diameter, l/x to Qjx; clad length, 30/* to 90/t; chords, 20ju, to 

 4:0(1. Endosomal spicules, filiform oxeas (fig. 18, ^) ; size 2/a by ( ?)it* 

 to 9fi by 2,000/i. Auxiliary spicules, anatriaenes (fig. 18, E) ; rhabd 

 diameter, 3ju, to 7fi; clad length, 20/a to 30/*; chords, 30/i to 40/x; rare 

 and location in sponge not certain. 



For all the above spicules, it will be noted there are few data as 

 to total lengths. This follows from the fact that in spite of utmost 

 care, it seems impossible to mount total spicules for this species. 

 They are not only exceedingly thin, long, and brittle, but also are 

 so interlaced that in disengaging any they are inevitably broken. 

 I should estimate that they were frequently over a centimeter long 

 and perhaps 2 or 3 cm. 



