72 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



U.S.N.M. No. 23010, My No. M. 390, collected at the same time and place 



as the preceding. 

 U.S.N.M. No. 23011, My No. M. 391, collected at the same time and place 



as the preceding. 

 U.S.N.M. No. 23012, My No. M. 392, collected at the same time and place 



as the preceding. 



At the time of collection, it was realized that these four specimens might 

 be conspecific, but they showed four types rather more different from one 

 another than is commonly found within a single species of sponge. Numer- 

 ous other specimens were observed in the field in this one locality, but all 

 fell into one or the other of four categories, illustrated by the four preserved 

 specimens. Histological study has indicated the essential inter-relationship. 



The shape is incrusting to massive, most of the specimens being under 

 3 mm thick ; but No. M. 391 reached a total thickness of 5 cm. The thicknesses 

 were often about 10 cm but spread laterally indefinitely. No. M. 390 was 

 growing on ramose coral and fairly well covered a bush-like structure. 



In life, all the specimens were a vivid dark rich brown on the exterior. 

 All were of the same color in the interior, with the exception of M. 392, of 

 which the endosome was orange, but M. 391 contained (in the endosome) 

 very numerous orange embryos, 300 /a in diameter. The consistency was 

 mediocre. 



The surface is punctiform with obvious pores, 200 p. to 300 ti in diameter, 

 and with about one pore per each square mm. It is paradoxical to note that the 

 thicker specimen is lipostomous so that on it no oscules are to be seen, 

 whereas they are obvious in specimens M. 389 and 392. Yet, in these it is not 

 so much that the oscule itself is obvious, having been closed at the time of 

 death, but rather that its location is marked by the convergence of a series of 

 grooves (due to exhalant canals) forming a stellate pattern. These oscules 

 are 1 to 2 cm apart. 



There is the usual haliclonid lack of ectosome. The endosome is a vaguely 

 isodictyal reticulation but is densely crowded with protoplasm, as in massalis, 

 and unlike most specimens of Reniclona. 



The skeleton consists exclusively of oxeas for spicules but also includes 

 obvious quantities of spongin. The latter not only connects spicules end to 



Text Figure No. 43. Three of the spicules (oxea) of Reniclona rotographura, X 781. 



